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Polymer Composites

Wiley Online Library : Polymer Composites

Published: 2018-02-01T00:00:00-05:00


The combined effects of wet–dry cycles and sustained load on the bond behavior of FRP–concrete interface


Effective bonding between the adherents plays a key point when dealing with the retrofit of concrete structures by using fiber-reinforced polymers (FRPs). However, lack of adequate studies on the long-term performance of the bond behavior of FRP–concrete interface under harsh environments will inhibit their application in the repair of aged structures. Therefore in this study, 60 double-lap shear-bonded FRP-concrete composite specimens were designed and tested under wet–dry cycles and sustained loading. The effect of FRP type (GFRP and CFRP), wet–dry cycling times (0–360 days) and sustained loading level (0–60% of the ultimate load of the control specimen) on the failure modes, stress transfer, and local bond-slip curves of the composite specimens were investigated. The experimental results showed that wet–dry cycling exposure changed the failure mode of the composite specimens from the concrete substrate to the adhesive–concrete interface, further extended the local debonding area and decreased the ultimate strains of composite specimens from 12,000 to 8,000 μɛ. The degree of the degradation will be further increased under the combined effect of sustained loading and wet–dry exposure. The effects of FRP type, wet–dry cycling times and sustained loading level on the fracture energy of the specimens were quantitatively analyzed. A regression model was then proposed that was able to predict the fracture energy after environment exposure with reasonable accuracy, which can provide a reference for the design of bond durability factors in relevant specifications, such as ACI 440R-08 POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Investigation of optical, film formation, and magnetic properties of PS latex/SP-MNPs composites


In this work, the optical, film formation, morphological and the magnetic properties of a novel type of nanocomposite system, composed of polystyrene (PS) latex and core-shell superparamagnetic nanoparticles (SP-MNPs), is presented. The film formation and optical properties were examined by UV-vis technique, morphological changes by scanning electron microscopy and magnetic properties studied using vibrating sample magnetometer (VSM) as a function of SP-MNPs content. A series of mixtures were prepared by mixing of PS latex dispersion with different amount of SP-MNPs in the range of (0–100 wt%). PS/SP-MNPs films were then prepared from these mixtures on glass substrates using drop casting method. After drying, film was separately annealed at elevated temperatures between 100°C and 250°C. In order to monitor film formation process, transmittance of these composites was measured after each annealing step as a function of SP-MNPs content. It was found that below a critical SP-MNPs content, PS percolates into the SP-MNPs hard phase and forms an interconnected network upon annealing. However, above this critical value, PS latexes were no longer film forming at all temperatures. Besides, composite films showed superparamagnetic behaviors. The saturation magnetization (Ms) first increased and reached to 0.014 emu/cm3 at 50 wt% SP-MNPs, then decreased to 0.010 emu/cm3 with increasing SP-MNPs content. The maximum value of Ms was approximately 0.020 emu/cm3 and was obtained for the 85 wt% SP-MNPs content film. These results indicated that the optical, film formation and magnetic properties of PS/SP-MNPs composite films can be readily tuned by varying SP-MNPs content. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Mechanical properties improvement and fire hazard reduction of expandable graphite microencapsulated in rigid polyurethane foams


Nowadays, reducing the fire hazard and improving the mechanical strength of rigid polyurethane foams (RPUFs) at the same time are important research direction in the fields of safety materials. Expandable graphite (EG) is an effective flame retardant for RPUF, but would destroy the compatibility of the matrix. In this article, EG is capsuled by melamine cyanurate (MCA) and then microencapsulated expandable graphite (MCEG) is obtained, which is added into RPUF. The mechanical properties of composites were evaluated by compressive strength test, torsion strength test and shear stress test. The fire characteristics including smoke and heat production of RPUF composites were studied using cone calorimeter test. And the thermal decomposition and flammable properties were further evaluated using thermogravimetric analysis and limiting oxygen index. The results show that the mechanical properties of RPUF containing MCEG are similar with RPUF and better than RPUF containing EG. Furthermore, MCA cover would impede expanding of EG, which weakens the protective and insulation effects of expanding layer. Therefore, the composites containing MCEG decompose faster and produce more smoke than the composites containing EG. However, MCA and EG have the synergistic enhancing effect on the flame retardant property of composite. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Microstructures and mechanical properties of thermoplastic composites based on polyarylate/nylon6 islands-in-sea fibers


Polyarylate (PAR) fiber-reinforced nylon6 composites are manufactured by molding uniaxially-aligned islands-in-sea fibers at different temperature (190–210°C), pressure (0.69–6.89 MPa), and time (1–10 min). For the purpose, the islands-in-sea fibers, in which 74 PAR islands act as reinforcing microfibers and nylon6 sea part serves as a semicrystalline matrix in the thermoplastic composites, are prepared by a conjugate melt-spinning. The tensile and dynamic mechanical properties of the thermoplastic composites are investigated by taking into account their microstructural and morphological features, which are influenced by the molding conditions, as examined by differential scanning calorimetry, 2D-X-ray diffraction, scanning electron microscopy, micro-CT, and polarized optical microscopy (POM) analyses. The thermoplastic composite manufactured at 200°C and 2.07 MPa for 3 min is found to have maximum tensile strength of ∼630 MPa and initial modulus of ∼70 GPa owing to multiple synergistic effects such as high crystallinity of nylon6 matrix, good alignment of PAR microfibers, interfacial crystallization of nylon6 on the reinforcing PAR microfibers, and low porosity. The findings of this study indicate that PAR/nylon6 inland-in-sea fibers can be utilized effectively for manufacturing high performance thermoplastic composites for sports, automotive, and protective applications. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Thermal and combustion features of rigid polyurethane biofoams filled with four forest-based wastes


In this study, four fillers from forest-based wastes were studied using thermogravimetry and contact angle measurements, and their compatibility with polyurethane were investigated by infrared spectroscopy performed in induced reaction mixtures, wherein the fillers were tested in the presence of excess isocyanate and catalyst. The fillers were then incorporated into rigid bio-based polyurethane foams (RPUFs), which were characterized using thermal and combustion analyses. Wood presented higher compatibility with the polyurethane system, leading to a copolymer formation comprised by urethane groups during its polymerization. Filled RPUF reached increased thermal and dimensional stabilities, and similar thermal conductivities and flammabilities compared with the neat RPUF. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Comparison on the properties of the wheat straw/rubber composites by adding graphite/carbon fiber


The conductive wheat straw/rubber composites (WSRCs) were prepared with wheat straw fiber (WSF), rubber compound and graphite powder (GP), or carbon fiber (CF). WSRCs with different loading of conductive fillers were prepared. The curing properties, mechanical properties, dynamic mechanical properties, morphology structure and conductive properties of the composites were investigated with reference to the conductive filler loading. Sodium hydroxide combined with bis-[γ-(triethoxysily)-propyl] tetrasulfide (NaOH-Si69-treated WSF) had a better bonding with the rubber matrix. The incorporation of GP and CF could restrict the mobility of matrix macromolecular chains and increase the viscosity of GP/CF-filled WSRCs, resulting in the increases in torque, stiffness and storage modulus and the slight reduction in scorch time and tensile strength as well as the damping behavior. Moreover, the conductivity of the WSRCs was increased significantly as the increase in filler loading. It was also found that the conductivity of GP-filled WSRCs were higher than that of the CF-filled ones. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

The effect of alkylated graphene oxide on the crystal structure of poly(4-methyl-1-pentene) during uniaxial deformation at high temperature


This work discussed the deformation-induced structure changes of poly(4-methyl-1-pentene)/alkylated graphene oxide (TPX/GO-ODA) nanocomposites during uniaxial stretching at a certain temperature (80°C). Based on crystalline behaviors of samples during deformation, the strain range could be divided into two regions. Within Region I, the melting temperature of TPX rose with strain; and the figures for TPX/GO-ODA were volatile; the crystallinity of these two samples showed a similar trend. Within Region II, melting points of two samples did not experience any remarkable changes; the figure for TPX/GO-ODA was higher than TPX. However, the crystallinity of two samples had a similar pattern; and the figures for nanocomposites showed a moderate increase and reached the plateau region at a greater strain. Wide-angle X-ray scattering demonstrated that crystal structure of samples could be destroyed during deformation. Small-angle X-ray scattering showed that the spherulitic structure of samples would transform into fibrillar structure. And the fibrillar structure size of TPX/GO-ODA was smaller than that of TPX according to Guinier approximation. All data revealed that GO-ODA not only prevented crystal structures from being destroyed within Region I, but also it might restrict rearrangements of molecular chains and crystal fragment within Region II. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Design and preparation of rapid full bio-degradable plastic composites based on poly(butylene succinate)


Rapid full bio-degradable plastic composites based on poly(butylene succinate) (PBS) were successfully designed and prepared. The bio-degradation behavior of the composites was focused on. Results demonstrated that the polymer composites incorporated with starch exhibited a rapid biodegradability. Only after 5 months of biodegradation, the polymer composites with 40 and 50 wt% starch were fully pulverized in the soil. However, mechanical properties of composites were also seriously deteriorated. Theory calculations and scanning electron microscopy confirmed the reason is the poor interface adhesion between PBS and starch. To address this issue, maleic anhydride grafted PBS (PBS-g-MAH) was prepared to use as the polymer matrix. As expected, the good mechanical properties were obtained due to an excellent adhesion in the interface. For instance, the tensile strength was increased from 15.0 to 23.0 MPa, and the impact strength is enhanced from 6.5 kJ/m2 to 11.9 kJ/m2 when the amount of MAH and dicumyl peroxide were 2 and 0.2 wt%, respectively. In addition, the use of PBS-g-MAH further increased the biodegradation rate of the composites. The PBS-g-MAH/starch (60/40) composites were fully pulverized in soil only after 3 months of biodegradation. Fourier transform infrared spectroscopy (FTIR) also revealed the compatibilizing mechanism between PBS-g-MAH and starch was that MAH reacted with hydroxyl groups in the starch to produce the ester. As an attractive full biodegradable polymer, the low-cost composites proposed here will have wide prospects of application in the near future. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Synergistic flame retardant mechanism of lanthanum phenylphosphonate and decabromodiphenyl oxide in polycarbonate


Lanthanum phenylphosphonate (LaHPP) was synthesized through solution reflux method with a hydrothermal reaction. The synergistic effect of decabromodiphenyl oxide (DBDPO) and LaHPP on thermal stability and flame retardancy of polycarbonate (PC) were investigated. Transmission electron microscope graphs showed that LaHPP dispersed well in the PC matrix. Thermogravimetric analyses indicated that the addition of LaHPP into PC/DBDPO composites led to better thermal stability. An appropriate content (1 wt%) of LaHPP could improve the UL94 rating (from V-2 to V-0) and limiting oxygen index value (from 32.8 to 40.5%) dramatically, and also brought an effective reduction in peak heat release rate and smoke release rate in cone calorimeter. Investigation of gaseous pyrolysis products and char residues demonstrated that LaHPP promoted the formation of more compact and solid chars, which acted as physical barriers to inhibit heat and oxygen transfer. The inside char layers also provided more space and time for DBDPO to play its flame retardant role in gaseous phases. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Development and characterization of zinc-incorporated montmorillonite/poly(ε-caprolactone) composite scaffold for osteogenic tissue-engineering applications


This article reveals the potential use of a macroporous 3D poly(ε-caprolactone)-zinc montmorillonite (PCL-ZnMMT) composite scaffold as a bone tissue engineering template. The zinc-incorporated porous scaffold was prepared by combining solvent casting and particulate leaching technique. Later, PCL-ZnMMT composite scaffolds were characterized for their physicochemical, mechanical and in vitro biological properties. Human adipose stem cells (hASCs) were utilized for in-vitro cell culture studies. Cell viability and proliferation of cell-scaffold constructs were investigated using the Alamar Blue and Live/Dead-staining assays. The osteogenic differentiation potential of hASCs on PCL-ZnMMT scaffolds was evaluated by the alkaline phosphatase assay; Scanning electron microscopy (SEM) was used to visualize mineral accumulation. X-ray diffraction results indicate that the incorporation of MMT into polymer matrix. Thermal gravimetric analysis showed that the presence of clay improves thermal stability of polymeric matrix. ICP findings showed that Zn ion concentration in the cell culture medium was at a sustainable range up to 7 days. SEM micrographs reveal that scaffold had a highly porous morphology and also the infiltration of cells into the porous structure. In vitro studies showed that the incorporation of Zn into the PCL-MMT system stimulated the in-vitro proliferation and osteogenic differentiation of hASCs. Findings indicate that PCL-ZnMMT scaffold composite may be a promising biomaterial for tissue engineering applications. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Multi-objective optimization of post-curing process for GNPs reinforced glass fabric/epoxy nanocomposite laminae


Post-curing processes are fundamental manufacturing operations for epoxy matrix composites from which high-quality parts are produced and see service in a great variety of industrial applications. Although many parameters affect these processes, only temperature is considered as affecting factor in most of the relevant studies. In this study, a multi-parameter design of experiments, using Taguchi method, has been conducted in order to investigate the optimum post-curing conditions for graphene nanoplatelets reinforced glass fabric/epoxy nanocomposite laminae. Both post-curing temperature Tpc and time tpc were treated as independent variables in a L9 Taguchi orthogonal array addressing three levels each. Ultimate tensile strength and strain at break were examined as pre-selected quality objectives. Through the multiple regression analysis performed, a highly accurate regression model was achieved for both optimization criteria. Finally, a multi-objective optimization genetic algorithm was used for the above models. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Modeling and simulation of nanocomposite based on poly propylene/graphene


The use of multi-scale model (MSM) which co-relates the microscopic and microscopic, temperature and morphology of crystals to each other is an important factor for determination of crystallinity in nanocomposite materials. Based on the MSM, an algorithm made of a combination of “finite volume method” (FVM) and the “pixel coloring method” (PCM) is mentioned. FVM technique is used in the large coarse grid for determination of macroscopic temperature degree and PCM is used for fine scale for investigation of the morphology of crystalline structure. In this article, role of cooling rate, the initial temperature and density of nucleation is studied. It is a novel study that is a combination of MSM with a multi-scale algorithm is utilized for investigation of nanocomposite crystallization. It is proved that nucleation rate is decreased by increasing temperature and consequently spherulites having larger sizes are created. In nanocomposite samples, latent heat is appeared at 240 K, contrasting in the case of pristine polymer. These phenomena are due to the fact that nanoparticles produce a very large number of nucleating sites. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Homogeneity quantification of nanoparticles dispersion in composite materials


As the quantitative evaluation of dispersion of nanoparticles are crucial for the research of nanocomposites, including ceramic, metal, and polymer nanocomposites, we proposed two quantifiable tools for the evaluation of dispersion in the nanocomposites by using machine-learning algorithms, that is the coefficient of variation of K-nearest neighboring distances (CVKD value) and the information entropy derived from the probability density function. In total 230 different type of dispersion morphologies of nanocomposites were investigated by using K-nearest neighboring algorithms, Gaussian mixture model, expectation maximization, and Kernel density estimation algorithms. The smaller values of CVKD or information entropy represented much more homogeneous dispersion of nanoparticles. It might be expected the information exhibited in the present study could assist in the rational design and fabrication of superior nanocomposites. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

New epoxy composite thermosets with enhanced thermal conductivity and high Tg obtained by cationic homopolymerization


Thermal dissipation is a critical aspect for the performance and lifetime of electronic devices. In this work, novel composites based on a cycloaliphatic epoxy matrix and BN fillers, obtained by cationic curing of mixtures of 3,4-epoxy cyclohexylmethyl 3,4-epoxy cyclohexane carboxylate (ECC) with several amounts of hexagonal boron nitride (BN) were prepared and characterized. As cationic initiator a commercial benzylanilinium salt was used, which by addition of triethanolamine, exhibited an excellent latent character and storage stability. The effect of the formulation composition was studied by calorimetry and rheological measurements. The variation of thermal conductivity, thermal stability, thermal expansion coefficient, and thermomechanical and mechanical properties of the composites with the load of BN filler (ranging from 10 to 40 wt%) was evaluated. An improvement of an 800% (1.04 W/m·K) in thermal conductivity was reached in materials with glass transition temperatures >200°C without any loss in electrical insulation. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Enhancing interfacial strength and hydrothermal aging resistance of silicone resin composites by different modification of carbon fibers with silica nanoparticles


Besides the well-designed combination of the fibers and matrix resin, the fiber-matrix interface plays a key role in bulk properties of composites. Here, the chemical grafting of silica nanoparticle (SiO2) onto fiber surface (CF-g-SiO2) using the bridging toluene-2,4-diisocyanate has been achieved and compared with the physical adsorption one (CF-ad-SiO2). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the covalent bonding nature between SiO2 and CF. By atomic force microscopy observation, coating or grafting SiO2 on the surface of CFs also enhanced fiber surface polarity and roughness. However, CF-g-SiO2 showed a better uniform distribution of SiO2 on the fiber surface compared with CF-ad-SiO2 with the serious agglomeration of SiO2. These results of dynamic contact angle measurements indicated that CF-ad-SiO2 and CF-g-SiO2 had the similar increase degree of surface free energy, which contributed to improve the wettability between CFs and matrix resin. Interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) showed great enhancements, especially for CF-g-SiO2 composites, which increased 10.92% in ILSS and 10.71% in IFSS compared with those of CF-ad-SiO2 composites. Moreover, the interfacial reinforcing mechanisms have also been studied. Additionally, the introduced Si-O-Si bonds at the interface by SiO2 coating or grafting resulted in the different improved degree of the hydrothermal aging resistance. The results showed that the quality of fiber-matrix interface could be tuned by varying the bonding natures between CFs and the modifiers, and chemically grafting SiO2 onto the fiber surface is the promising multifunctional reinforcement. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Synthesis and characterization of flexible/stretchable polyimide having long/bulky aryl pendent group and polyimide/silicon dioxide nanocomposites.


A new diamine monomer having ether and azomethine linkages in the long pendent group was synthesized. New polyimide was prepared by reacting the new diamine with BTDA and nanocomposites were prepared with silicon dioxide as nanofiller. SEM analysis shows a uniform distribution of the nanopowder in the polyimide matrix. TGA shows that the polyimide and nanocomposites have good thermal stability with the T10% values varying between 440 and 458°C. DSC analysis shows Tg values between 210 and 230°C. The neat polyimide shows high elongation at break and stretchability (260%) but low tensile strength. The nanocomposites of polyimide show lower elongation at break but have improved tensile strength. The chemically imidised polyimide shows good solubility in solvents like N, N-dimethyl formamide, N, N-dimethyl acetamide, and N-methyl 2-pyrrollidone. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Experimental and numerical investigations of kenaf natural fiber reinforced composite subjected to impact loading


The aim of this work is to develop a Finite Element Model based on continuum damage mechanics to predict the structural response of Kenaf composite when subjected to high-velocity impact. The stress–strain response of the Kenaf composite through the fiber direction was simulated to examine prediction accuracy of this simulation approach. A combined elastic-damage material model, incorporating the 3D Hashin's failure criteria, was implemented into the ABAQUS/Explicit finite element code by user-defined VUMAT material subroutines. The results from the model predictions were compared with experimental data obtained by SHPB compression testing. The developed Finite Element Model of the full-scale test presented an accurate prediction of the strain waves in the bars and successfully replicated the structural impact response of Kenaf composite over the range of impact loadings studied. The model also provides a reasonably good agreement between numerical and experimental results on the effect of strain rate on the failure stress and failure strain. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Development and mechanical characterization of composites based on unsaturated polyester reinforced with maleated high oleic sunflower oil-treated cellulose fiber


This work studies the effect of surface functionalization of chopped cellulose fibers (CFs) on the mechanical properties of unsaturated polyester (UPE) matrix-based composites. Surface functionalization of CFs was carried out by treating them with maleated high oleic sunflower oil (MHOSO) solutions at concentrations of 2.5, 5, and 10 vol.%. Untreated and MHOSO-treated CFs were dispersed in UPE at 1, 2, and 3 wt% by mechanical mixing. Fourier transform infrared spectroscopy confirmed successful functionalization of CF with MHOSO. Scanning electron microscopy revealed that MHOSO-treatment improved dispersion of the fibers in UPE. Tensile and compressive testing of the composites showed that MHOSO -treated CF improved the strength of the composites compared with untreated CF. This was attributed to better dispersion of the former cf. the latter. Increasing the extent of functionalization of CF with MHOSO resulted in increased strain to failure of the composites due to the MHOSO acting as a plasticizer. MHOSO -treated CF increased the hydrophobicity of the composites compared with untreated CF, thereby offering protection against moisture-induced degradation. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

The use of upconversion microparticles as a novel internal radiation source for fabrication of composite materials


Upconversion (UC) microparticles were used as novel internal radiation sources for composite preparation. These particles emit Ultraviolet-Visible radiation when exposed to Near-infrared waves. This radiation causes uniform and deep polymerization. Two types of UC particles were prepared via a facile hydrothermal method, including NaLuF4: Yb 20%, Tm 0.5% and NaLuF4: Yb 40%, Tm 0.5%. The effect of three different photoinitiator systems, including titanocene, bisacylphosphine oxide, and camphorquinone, on the cure depth and the degree of conversion (DC) was investigated. Polymerization reaction rate was also studied. Moreover, the effect of weight percentage of UC particles and laser intensity on the cure depth and the DC were evaluated. Rheological behavior of the composites with different percentage of the particles (1, 3, and 5%) and the effect of temperature were studied. The results showed that the overlap of the UC particles emission spectrum with the photoinitiator absorption spectrum and the intensity of the photoinitiator absorption in the emission range of the particles are of the most important factors affecting cure depth, rate and DC. The cure depth with DC up to approximately 80% was 41 mm. Moreover, the DC was almost constant along the sample. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Compressibility measurement of composite reinforcements for flow simulation of vacuum infusion


In flow simulation of liquid composite molding under a flexible cover, such as vacuum infusion (VI), the accuracy can be improved by accounting for the compressibility of the reinforcement. The compressibility has been predominately measured using a universal testing machine (UTM) but discrepancies have been observed between the compressibility determined by UTM testing and that in situ during VI processing. The differences between the two are thought to be due to (1) differences in hydrodynamic loading and (2) precision difficulties related to the small displacements being measured. In situ VI compressibility characterization is more difficult and requires specialized equipment. This study aims to validate the use of UTM-measured compressibility in VI flow simulation, by investigating the agreement between the two measurement methods, and to develop an experimental methodology to optimize that agreement. Wet UTM testing was instrumented with pressure sensors, which allowed for a thorough investigation of the validity of model predictions of the fluid pressure. Matching the test conditions, as well as careful thickness calibration, resulted in good agreement between dry UTM and VI compressibility. Dry UTM testing resulted in better agreement with VI than wet UTM testing. This suggests that dry UTM measurement of the compressibility is sufficient and wet testing is ultimately unnecessary for the purposes of flow simulation. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Is there any way to simultaneously enhance both the flame retardancy and toughness of polylactic acid?


Nowadays, numerous works have been undertaken to improve the fire resistance of polylactic acid (PLA). However, the presence of flame retardant usually shows a great destruction on the mechanical properties of PLA matrix, especially the toughness. This paper presents a new approach to simultaneously enhance both the flame retardancy and toughness of PLA by incorporating polyurethane-microencapsulated ammonium polyphosphate (MCAPP). The prepared MCAPP was blended with PLA by melt compounding to prepare PLA/MCAPP composites. The results indicated that the introduction of 15% MCAPP increased the limiting oxygen index of PLA composites from 19.3% to 28.3%, upgraded the UL-94 rating from no rating to V-0, and decreased the peak heat release rate from 464.2 to 332.2 kW/m2. Even though the tensile strength of PLA composites was decreased to 53.8 MPa, the toughness was significantly improved, with elongation at break lengthened to 40.8% and notched impact strength increased to 2.95 kJ/m2. The possible mechanisms for both flame retardancy and toughness were also discussed. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Influence of poly(p-phenyleneterephalamide) pulp by surface modification with dopamine to nitrile butadiene rubber


Nitrile butadiene rubber (NBR) is widely used in the production of oil and fuel-resistant rubber parts. Poly(p-phenyleneterephalamide) (PPTA) pulp is used as a reinforcing fabric in NBR composites to improve its mechanical properties despite the weak bonding between NBR and PPTA pulp. In this work, PPTA pulp was modified by interfacial polymerization of dopamine (DOPA). A surface-adherent poly(dopamine) (PDA) film was formed on the surface of the PPTA pulp, which improved bonding to NBR and mechanical properties of the prepared composites. The surface of the modified PPTA pulp was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results demonstrate that PDA was successfully functionalized on the PPTA pulp and that the surface of the composite was rougher after modification. The effects of treatment conditions on the mechanical properties of NBR/pulp composites were also investigated. The tensile strength markedly improved with treating time of 30 h at a DOPA concentration of 2 g/L. Strong interactions, including hydrogen bonding and adsorption, play an important role in the tensile strength of the material. Our results demonstrate that surface modification by PDA is beneficial for improving the strength of the NBR matrix. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Correlation between failure and local material property in chopped carbon fiber chip-reinforced sheet molding compound composites under tensile load


To develop further understanding towards the role of a heterogeneous microstructure on tensile crack initiation and failure behavior in chopped carbon fiber chip-reinforced composites, uni-axial tensile tests are performed on coupons cut from compression molded plaque with varying directions. Experimental results indicate that failure initiation is relevant to the strain localization, and a new criterion with the nominal modulus to predict the failure location is proposed based on the strain analysis. Furthermore, optical microscopic images show that the nominal modulus is determined by the chip orientation distribution. At the area with low nominal modulus, it is found that chips are mostly aligning along directions transverse to loading direction and/or less concentrated, while at the area with high nominal modulus, more chips are aligning to tensile direction. On the basis of failure mechanism analysis, it is concluded that transversely oriented chips or resin-rich regions are easier for damage initiation, while longitudinally oriented chips postpone the fracture. Good agreement is found among failure mechanism, strain localization and chip orientation distribution. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Mechanical properties and slurry erosion resistance of a hybrid composite SiC foam/SiC particles/EP


A novel hybrid composite SiC foam/SiC particles/EP (denoted as SiCfoam/SiCp/EP), consisting of E-51 epoxy resin as the matrix, SiC foam and SiC particles as the reinforcements, was prepared in this work. The slurry erosion properties of SiCfoam/SiCp/EP composite and SiCfoam/EP (SiC foam/epoxy resin) composite were investigated by using a rotating disc rig. It was found out that SiCfoam/SiCp/EP exhibited better mechanical and anti-erosive performance as compared with SiCfoam/EP. SiC particle size had great influence on the mechanical and anti-erosive properties of the hybrid composites. Smaller SiC particles were beneficial to improve the mechanical strength, but inclined to decrease the anti-erosive performance of the composite. In general, the hybrid composite SiCfoam/SiCp/EP can be applied potentially with the excellent anti-erosive performance under the solid particle erosion conditions. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Effect of carbon fiber-graphene oxide multiscale reinforcements on the thermo-mechanical properties of polyurethane elastomer


Thermo-mechanical properties are often the bottleneck for advanced applications of polyurethane (PU) elastomer materials. Carbon materials are emerging as promising reinforcing fillers for polymers due to their superior mechanical and conductive properties. In this study, carbon fiber-graphene oxide (CF-GO) multiscale reinforcements are fabricated for improving thermal-mechanical properties of PU elastomers. To this end, CFs are firstly modified with GO via electrophoretic deposition and subsequently cooperate with free-dispersed GO sheets in PU matrix. This multiscale reinforcing strategy effectively improved thermo-mechanical properties and thermal stability of PU elastomer due to the improved CF-PU interfacial interaction as well as the local stiffening of fiber-matrix interphase by the dispersed GO sheets. This reinforcing approach also led to a synergistic increase in the thermal diffusivity of PU elastomer due to the formation of interconnected conductive network, in which CFs serve as a conductive framework that connects the free-dispersed GO sheets. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Synergistic toughening of nanocomposite hydrogel based on ultrasmall aluminum hydroxide nanoparticles and hydroxyapatite nanoparticles


The development of hydrogels combining superior mechanical property attracts researchers' attention in recent years. Here, a novel nanocomposite hydrogel is prepared by one-step photo-polymerization of acrylic acid (AA) and N,N-dimethylacrylamide (DMAA) in the presence of hydroxyapatite nanoparticles (HAp NPs) and aluminum hydroxide nanoparticles (Al(OH)3 NPs). The resulting transparent hydrogel exhibits ultrahigh toughness of 28.3 MJ m−3, high strength of 2.8 MPa, large elongation of 1300%, excellent self-recovery and good biocompatibility. The crosslinking mechanism is contributed to the ionic coordination interaction between cations absorbing on the surface of nanoparticles and carboxyl groups of the polymer chain, and the synergistic toughening effect between HAp NPs and Al(OH)3 NPs is responsible for improving the strength and toughness simultaneously. Furthermore, this synergistic toughening strategy may provide a universal method for designing and constructing high strength nanocomposite hydrogels in many applications, especially for artificial cartilages. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Thermo-mechanical characterization of shape-memory polyurethane nanocomposites filled with carbon nanotubes and graphene nanosheets


The shape-memory materials are nowadays an important subject in the scientific community due to their huge technological potential. In the present study, in order to pursue the mechanical reinforcement and improvement of the shape-memory thermoplastic polyurethane (TPU) properties, it was conducted an experimental study in which TPU nanocomposites containing carbon based nanoparticles were produced by melt mixing and injection molding. The resulting nanocomposites contained treated and non-treated multiwalled carbon nanotubes and graphene. A morphological, thermal and mechanical characterization was performed and in all the samples tested an enhancement on the thermo-mechanical properties could be observed whenever the pure TPU was concerned. The thermal characterization performed enables to observe that carbon like reinforcement contributes positively to a better heat transfer diffusion. Furthermore, graphene seems to be the most promising reinforcement, when assessing solely the mechanical properties of the obtained nanocomposites. Overall, carbon like reinforcement at the nanoscale on a TPU matrix seems to enhance the shape-memory ability of the pure TPU material. Nevertheless, the latter requires further insight. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Abnormal mechanical properties of composites based on boron oxide oligomer/polyethylene blends


The mechanical properties of composites based on the inorganic boron oxide oligomer (BOO) and low-density polyethylene (LDPE) produced by extrusion and injection molding have been studied in the range of volume fractions of the inorganic component from 0 to 64 vol%. An abrupt increase in the Young's modulus and ultimate tensile strength of the composites in the vicinity of 30 vol% BOO has been found. These critical properties are accompanied by a stepwise decrease in the elongation at break at the same volume fraction of the inorganic component. The mechanical properties of BOO/LDPE composites were compared with the same characteristics of composites based on LDPE and polymethyl methacrylate prepared via a similar way. The electron microscopic examination has suggested that the abnormal concentration dependences of the Young's modulus, tensile strength, and elongation at break of BOO/LDPE composites are conditioned by the formation of the unidirectional microfibers of the inorganic oligomer as soon as its volume fraction exceeds the critical threshold. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Effect of pre-tension on tensile strength of glass fibers-epoxy composite reinforced with shape memory alloy wire


In this study, the potential of superelastic shape memory alloy (SMA) wire to enhance the tensile strength of a glass fibers reinforced epoxy composite was evaluated. Composite specimens with one embedded SMA wire fabricated with hand-layup method. The specimens were placed under tensile loading (pre-tension) and unloaded before ultimate tensile strength. The pre-tension amounts were 65, 75, and 85% of ultimate tensile strength. After unloading, SMA wire wants to transform to the austenite phase and recover its primary shape and a large amount of compressive stress will be released over the composite specimens. Results show that the ultimate tensile strength for specimen with 75% pre-tension was 32% higher than the composite without pre-tension. This pre-tension has the best effect on ultimate tensile strength and pretension of specimens before ultimate tensile strength leads to higher tensile strength due to the high superelasticity of the SMA wires. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Positron lifetime study of PAN-based carbon fiber-reinforced polymer composites


Microstructural characterization of polyacrylonitrile-based carbon fiber (PAN-CF) reinforced polybutylene terephthalate (PBT) and polyethersulfone (PES) polymer composites have been performed. The positron lifetime parameters viz., o-Ps lifetime (τ3), o-Ps intensity (I3) and fractional free volume (Fv) of PAN-CF reinforced PBT (PBT/PAN-CF) and PAN-CF reinforced PES (PES/PAN-CF) composites are correlated with the mechanical properties. The fractional free volume obtained experimentally show negative deviation from the linear additivity relation in PBT/PAN-CF composites for lower wt% of PAN-CF loading. This indicates the improved adhesion between PAN-CF and polymeric chains of PBT matrix in PBT/PAN-CF composites. The positive deviation of fractional free volume (Fv) in PES/PAN-CF composites suggests the formation of interface between PAN-CF and polymeric chains of PES matrix. The increased glass transition temperature (Tg) of PBT/PAN-CF composites suggests the reduced main chain and segmental mobility of PBT polymeric matrix by the presence of PAN-CFs. The decreased glass transition temperature (Tg) in PES/PAN-CF composites indicates the reduced molecular packing due to interface formation. The increased crystallinity and improved mechanical properties of PBT/PAN-CF and PES/PAN-CF polymer composites are attributed to the increased nucleation density of carbon fibers in the composites. The FTIR results suggest the improved chemical interaction between the functional groups of PAN-CF and PBT matrix. The hydrodynamic interaction is also high in PBT/PAN-CF than PES/PAN-CF composites. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Reinforcement of epoxidized natural rubber through the addition of sepiolite


Sepiolite reinforced epoxidized natural rubber (ENR) composites were prepared by incorporation different loadings of sepiolite. Curing characteristics, mechanical properties, morphology and thermal stability of sepiolite-filled ENR composites were studied. Adding sepiolite into ENR has resulted in remarkable improvement of curing characteristics, mechanical properties and thermal stability. This is attributed to the unique structure of sepiolite itself. It gives a greater interaction between hydroxyl and/or siloxane groups of sepiolite and epoxide segment of ENR. The mechanical properties are very good agreement to the SEM micrographs where more surface roughness is observed upon the addition of sepiolite. Further evidence was found for the thermal decomposition temperature of the composites. The obtained thermogravimetric profiles indicate that their thermal stability was clearly enhanced irrespective of sepiolite loadings. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Toughness of Scots pine - polymethyl methacrylate composite


A series of 1,600 samples of the sapwood of Scots pine (Pinus sylvestris), part of them in natural state, but majority subjected to polymerization with various level of impregnation with methyl methacrylate, were tested for toughness on Charpy's impact machine. The goal of the experiment was to investigate how polymerization improves toughness and, additionally, how exposure to low temperatures and to the action of seawater influences this property of the material tested. It was found that within impregnation levels and temperatures tested variability of toughness due to these two factors is almost linear and in practical considerations may be predicted based on an empirical formula. It was also found that exposure to the action of seawater weakens the material. To verify anisotropy of toughness in the plane perpendicular to the grain all samples were consistently cut out such that one pair of opposite lateral faces were tangent to the growth rings. Half of the whole set of samples was fractured with an impact directed perpendicular to the growth rings and the other half with an impact directed in the tangential direction. The results show that although in general toughness is slightly higher in the direction perpendicular to the growth rings than in the tangent direction, the difference may be neglected in practical considerations. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

An investigation on the reinforcement mechanism of the nano-sized carbonaceous filled epoxy-glass fiber hybrid-composites through analysis of fracture surfaces


The objective of this work was to investigate the influence of delamination degree of the graphite on the mechanical properties of glass fiber/epoxy composite. To aim this, graphene and highly expanded graphite (HEG) nanofillers were synthesized using intensive ultrasonic method and were added to the epoxy and also glass fiber/epoxy composite, separately. Subsequently, tensile, flexural and impact strength of prepared samples were studied. Furthermore, the lateral size and dispersion quality of synthesized fillers in the epoxy matrix was inspected through using field emission scanning electron microscopy. Mechanical results demonstrated an enhancement by addition of both synthesized nanofillers to both nanocomposites and hybrid-composites. Highest increment rate of tensile strength was related to the nanocomposites containing 0.5 wt% nanofillers in which 61 and 51% enhancement for graphene nanoplate and highly expanded graphite loaded samples, respectively, was observed compared with the neat epoxy. It was found that, degree of delamination and dispersion of graphite platelets has a fundamental influence on the mechanical properties. In addition, fracture surface of epoxy nanocomposites and hybrid-composites were inspected to study the toughening mechanism. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Quantitative evaluation of the effect of dispersion techniques on the mechanical properties of polyhedral oligomeric silsesquioxane (POSS)–epoxy nanocomposites


This experimental study investigates the effects of dispersion techniques on the mechanical properties of POSS-epoxy nanocomposites. The POSS is dispersed into the epoxy resin by stoichiometrically varying the weight fraction from 0.5 to 10 wt% and materials are prepared using three different dispersion techniques. Various mechanical properties are reported as functions of processing parameters and weight fractions. It is found that the nanocomposites with highly dispersed POSS show higher modulus and toughness values. For example, nanocomposites prepared by ultrasonication show increases in elastic and flexural modulus values by average amounts of 23% and 15%, respectively. Also, it is found that fracture toughness values increased for all three processing techniques, with the highest increase by an average of 50% at 8 wt% of POSS inclusion for nanocomposites prepared by ultrasonication. TEM images of the nanocomposites demonstrate that the properties are also affected by the formation of soft domains at higher loading levels of POSS. Further evidence on the soft domains is found in the variations of Tg. FTIR spectroscopy shows evidence of SiOSi stretching, again suggesting the formation of compliant domains due to POSS-POSS agglomeration. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Evaluation of viscoelastic, thermal, morphological, and biodegradation properties of polypropylene nano-biocomposites using natural fiber and multi-walled carbon nanotubes


This article investigates the performances of polypropylene/kenaf fiber/polypropylene-grafted maleic anhydride/multiwall carbon nanotube (PP/kenaf/PP-g-MA/MWCNT) nano-biocomposites in terms of viscoelastic, thermal, and biodegradability properties. Nano-biocomposites with kenaf weight content of 30 wt%, fiber length of 6 mm and different contents of MWCNTs (0.5–2 wt%) were produced for testing and characterization. The samples were made by melt compounding in Brabender internal mixer and then hot and cold pressing. The dynamic mechanical thermal analysis results showed that the incorporation of MWCNT enhanced the storage and loss moduli of the PP/kenaf/PP-g-MA biocomposites. Differential scanning calorimetry results depicted an increase in the melting and crystallization temperatures of PP/kenaf/PP-g-MA biocomposites with the increase of MWCNT contents. The biodegradation of biocomposites was investigated in the activated sludge on a laboratory scale for 10 months in order to study the rates of biodegradation of the samples. The biodegradability test conducted on each specimen illustrated that the produced biocomposites are subjected to partial biodegradation, judging by the change in mechanical properties and weight of them after the test. Morphological study which characterized using scanning electron microscopy technique verified that a good and homogeneous distribution of MWCNT through the biocomposites; however; some aggregates were revealed at higher MWCNTs content. POLYM. COMPOS., POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Tuning morphology and mechanical property of polyacrylamide/Laponite/titania dual nanocomposite hydrogels by titania


The tough polyacrylamide/Laponite/titania (TiO2) dual nanocomposite (NC) hydrogel was fabricated by in situ radical polymerization of acrylamide (AAm) in the dispersion of Laponite and TiO2. TiO2 nanoparticles were prepared by sol-gel method and used as both the inorganic filler and multi-functional crosslinking agent. The morphology of hydrogel was tuned as functions of the sodium hydroxide (NaOH) concentration and the ratio of Ti (mmol) to clay (g) (mmol Ti/g clay). SEM and HR-TEM morphologies revealed that Laponite and TiO2 tended to form a uniform and regular microstructure like peasecod in poly(acrylamide) (PAAm) matrix due to the synergistic effect between electrostatic interaction and covalent interaction when the concentration of NaOH used in TiO2 hydrosol increased to 1 × 10−1 mol/L. This homogeneous microstructure enhanced mechanical properties of hydrogel. The compression strength, modulus and fracture energy reached 2,107 kPa, 247 kPa, and 1,837 J/m2, respectively. The gels exhibited excellent fatigue resistance and good UV protective performance. It might have potential application in optical materials, wound dressing materials and tissue engineering scaffolds. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Hybrid Pla/wild garlic antimicrobial composite films for food packaging application


Composite films based on poly(lactic acid) filled by 0.5 and 5 wt.% of Allium ursinum extract (wild garlic) for food packaging applications were prepared. Obtained films were examined from the view of characterization material properties and antimicrobial potential. The addition of two different amounts of A. ursinum extract improved thermal and mechanical properties of neat PLA (increase in Tg and tensile strength for both loadings). The oxygen barrier properties of the obtained hybrid films in dry condition were not significantly modified, while a slight increase of oxygen transmission rate was observed for the 5% loaded samples. Differences were detected in ΔE* values among the films containing A. ursinum extract in comparison with neat PLA. A marked difference between neat PLA and sample with 0.5 wt% of A. ursinum extract (3-6) was observed, while the color of the samples with 5 wt% was characterized by a completely different shade compared with neat PLA (>12). The antimicrobial activity of PLA films (neat and with 0.5 and 5 wt% of A. ursinum extract) was tested against Gram-negative bacterium Escherichia coli and both polymer composites with 0.5 and 5 wt% AU extract showed antimicrobial activity. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Well-dispersed polyurethane/cellulose nanocrystal nanocomposites synthesized by a solvent-free procedure in bulk


Polyurethane (PU) nanocomposites utilizing cellulose nanocrystals (CNCs) as nanofiller and amorphous PU matrix were synthesized in a novel solvent-free bulk process. A green nanofiller, CNCs, was studied as reinforcement and was further modified by grafting poly(ethylene glycol) (PEG) on the CNC surface (CNC-PEG). Transmission electron microscopy revealed an excellent dispersion of the PEGylated CNC nanoparticles in the PU matrix, whereas as-received CNCs formed agglomerates. The results indicated strong improvements in tensile properties with Young's modulus increasing up to 50% and strength up to 25% for both, PU/CNC and PU/CNC-PEG nanocomposites. The enhanced tensile modulus was attributed to stiff particle reinforcement together with an increase in glass transition temperature. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Influence of maleated polypropylene coupling agent on mechanical and thermal behavior of latania fiber-reinforced PP/EPDM composites


The influence of maleated polypropylene (MAPP) on the mechanical/thermal properties of short latania fiber-reinforced poly(propylene)/ethylene-propylene-diene-monomer (SLF/PP/EPDM) composites was investigated. Two different MAPP weight percentages (0 and 2wt%) and five different fiber weight contents (0, 5, 10, 20, and 30wt%) were considered, where the density of MAPP at the fiber surfaces progressively decreased. For a given fiber loading, addition of 2wt% MAPP led to roughly a 3–9% increase in tensile/flexural moduli and strengths over SLF/PP/EPDM composites with no MAPP. Moreover, composites containing MAPP displayed a profound improvement (37–78%) in impact energy absorption. In addition, composite heat deflection temperatures notably increased by 3–4°C with MAPP addition. Microscopic imaging suggested that matrix crazing, fiber pull-out, and fiber fractures were key failure mechanisms. Hence, SLF/PP/EPDM composites modified with 2%wt MAPP may serve as a low cost alternative to other natural fiber thermoplastic composites. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Preparation of mesoporous SBA-15/polymer-copper(II) composites in supercritical CO2 and their multiple applications


Novel organic–inorganic mesoporous SBA-15composites containing nitrogen heterocyclic ring–copper complexes were prepared in supercritical carbon dioxide. Fourier transform infrared spectroscopy revealed that the composites consisted of SBA-15 and poly(Pya-co-AA)–Cu(II). X-ray diffraction results indicated that the obtained composite possessed a two-dimensional hexagonal-ordered mesoporous structure. The specific surface areas of the composites were determined by Brunauer–Emmett–Teller method during nitrogen gas adsorption. The morphology of the composite was characterized by transmission electron microscopy. The effects of operating parameters, such as pressure, adsorption time, and monomer concentration, were also investigated. High-yield, uniform composites with large aspect ratios were obtained at moderate concentration and pressure at a certain time. In addition, the adsorption behaviors of bovine serum albumin and the catalytic oxidation of benzylalcohol by the composites were evaluated. The adsorption capacities and catalytic performance of composites were 442.5 mg L−1 and 54.4%, respectively. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Degree of Crystallinity and β Phase Fraction of Polyvinylidene Fluoride Nanocomposites Containing Ionic Liquid and Graphene/Carbon Nanotube


Bucky gel actuator (BGA) is a type of electro-active polymer that bends when stimulated by an electric field. Its operation is affected by a matrix network, which has two opposite effects on ion migration and material strength properties of the actuator. Therefore, designing a BGA with more deflection or more strength demands the study of matrix structural properties. In this paper, polyvinylidene fluoride (PVDF) was used as the polymer matrix in BGA composites, and the degree of crystallinity and the fraction of β phase were calculated using X-ray diffraction and Fourier Transform Infrared spectroscopy respectively to investigate the matrix structural properties. Furthermore, Raman spectroscopy analysis was utilized for phase characterization. Several composite films with various components including electrode and electrolyte layers of BGA were prepared by the drop-casting method in two different conditions to study the effects of PVDF concentration in dimethylacetamide solvent, drying temperature, and additive materials on the matrix structural properties for the first time. It was observed that low concentrations of PVDF in dimethylacetamide solvent coupled with a high drying temperature in a carbon nanotube-based BGA in contrast with using a graphene-based BGA, had the lowest degree of crystallinity and β phase fraction. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

The roles of interphase and filler dimensions in the properties of tunneling spaces between CNT in polymer nanocomposites


In this article, the properties of tunneling mediums between adjacent nanotubes in polymer carbon nanotubes nanocomposites are investigated assuming the main tunneling mechanism of electrical conductivity. The tunneling distance is expressed as a function of filler and interphase dimensions by the roles of these parameters in percolation threshold and effective filler fraction. In addition, the tunneling resistance and conductivity are defined based on the tunneling distance. The properties of tunneling spaces are determined in some samples and their variations at different ranges of parameters are analyzed. It is found that the addition of filler concentration decreases both tunneling distance and resistance. Also, low percolation threshold and high filler concentration are necessary to reduce the tunneling distance and resistance. Moreover, thin nanotubes, low waviness, thick interphase and long nanotubes cause desirable properties for tunneling mediums. According to this analysis, short tunneling distance and low tunneling resistance create high conductivity in polymer nanocomposites. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Eco-friendly composites derived from naturally occurring molecules in promoting dispersion of nanosized silica particulates


The reinforcement of highly dispersible silica (HDS) in Natural rubber was hindered by their high polarity and hydrophilic surface of the filler. We addressed this challenge by developing a Terpene phenolic resin functionalized Natural rubber (TNR) coupled with epoxidized natural rubber (ENR) composites. The loading of the HDS were considered from 40 to 60 phr (parts per hundred rubber). The uniform distribution of the HDS within the rubber blends in the absence of silane coupling agent and process oil was proven by cure characteristics, physico-mechanical properties, air ageing, dynamic mechanical analyses, Payne effect, contact angle, DeMattia flexing, dielectric properties and transmission electron microscopy. Overall, these newly developed green composites are superior to that of the reference composite, using process oil and TESPT (Bis-(triethoxysilylpropyl) tetrasulfide) as a coupling agent. Dispersion of HDS in rubber matrix may interfere with the addition of Zinc Oxide Nano particles (Nano-ZnO) due to the alkali-acidic reaction. Thus, this study explores the importance of omitting Nano-ZnO during internal mixing stage but incorporation of the same with the curing additives on a two roll mill. Our findings open up a new avenue to a fundamental understanding of HDS interaction in the novel green composites. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Natural fiber reinforced polylactic acid composites: A review


Biopolymer-based composites have attracted the attention of researchers and industries due to their eco-friendliness and environmental sustainability, as well as their suitability for a number of applications. Biocomposites containing natural fibers and biopolymers would be the ideal choice in the development of biodegradable materials for different applications. Polylactic acid (PLA) is an environmentally interesting biopolymer, which also has exclusive qualities, such as good transparency and processability, glossy appearance, and high rigidity, although it has some shortcomings as well, for example, its brittleness and high rate of crystallization. PLA-based natural fiber composites are entirely bio-based materials with promising biodegradability and mechanical properties. Several research studies have been carried out on PLA and its composites to explore their potential to substitute petroleum-based products, but until now there is no comprehensive review with up-to-date research data available in the literature. The aim of this review is to highlight the trends in the research and development of PLA and PLA-based natural fiber composites over the past few years. This review article covers current research efforts on the synthesis and biodegradation of PLA, its properties, trends, challenges and prospects in the field of PLA and its composites. PLA-based composites are moderately abundant; and further research and development is needed for cost reduction and broader utilization. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Thermo-mechanical and shape memory behavior of TPU/ABS/MWCNTs nanocomposites compatibilized with ABS-g-MAH


Thermo-mechanical and shape memory behavior of melt processed TPU/ABS (80/20 w/w) blends compatibilized with varying amounts of ABS-g-MAH loaded with multiwalled carbon nanotubes (MWCNTs) were discussed. The morphological observations by SEM and TEM techniques confirmed that introduction of ABS-g-MAH leads to a significant reduction in the size of ABS domain size due to improvement of interfacial adhesion between the blend components. Incorporation of MWCNTs to the compatibilized blend resulted in further reduction of the ABS droplet size. Mechanical properties investigations revealed that tensile strength of the TPU/ABS blend being about 26.4 MPa increases to 44.6 MPa, that is, about 70% improvement, on incorporation of 6 wt% ABS-g-MAH to the noncompatibilized blend. In the same direction, Young's modulus increases ca. 13%. A significant enhancement of about 70% in Young's modulus of the compatibilized blend was observed by inclusion of 2 wt% MWNCNTs. The shape memory results showed that interfacial compatibilization process has a strong positive impact on the shape recovery and shape fixity ratio of the blends. Moreover, loading MWCNTs into the compatibilized blend further improved these features. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Tailoring the properties of a polymer nanocomposite with a magnetic field


The properties of nanocomposites can be tailored by organizing nanoparticles within the polymer matrix, that is, for potential aerospace, automobile, and infrastructure applications. Multiwalled carbon nanotubes are coated with nickel to produce hybrid Ni-MWNT nanoparticles. These magnetized nanoparticles are introduced into an epoxy matrix at a relatively low 0.25%–1% volume fraction and oriented along particular directions with an external magnetic field . Changing this alignment makes it possible to tailor the properties of the resulting composite material, that is, its tensile strength, microscopic elastic modulus, and electrical resistivity. The alignment imparts anisotropic properties to the bulk material, but when the nanoparticles are aligned in perpendicular directions in two sequential layers, this coupled orientation produces an overall isotropic composite material. The tensile strength of a nanocomposite containing 0.25 vol% of aligned Ni-MWNT nanoparticles is ∼9% higher than of pure epoxy. Its AC electrical resistivity along the alignment direction is reduced by ∼20% in comparison with an epoxy composite containing a similar volume fraction of randomly dispersed nanoparticles. These outcomes reveal that, even at a relatively low nanoparticle volume fraction, the alignment of Ni-MWNTs in epoxy with an external magnetic field induces property anisotropy, which can be tuned through multidirectional alignment. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

A facile method to prepare nanoscale polyacrylonitrile particles grafted aramid fibers for superior interfacial and mechanical properties of epoxy composites


A very simple and efficient method was developed to improve the interfacial properties of aramid fibers reinforced composites. The aramid fibers and the acrylonitrile (AN) monomers were mutually irradiated by γ-ray in cyclohexane solution, initiating AN to polymerize on the fibers surface. Surface morphologies, chemical structure, mechanical behavior, thermal stability of the polyacrylonitrile (PAN) grafted aramid fibers and interfacial properties of their composites were systematically characterized. The results indicated that the linear PAN fantastically united to be nanoscale particles with 200 nm size, and grafted on the aramid fibers surface uniformly and compactly. Despite a slight decrease with 4°C in fiber heat resistance, the mass loss of the PAN-grafted fibers significantly reduced. Surprisingly, the interfacial shear strength of PAN grafted aramid fibers improved by 71.50% from 36.33 ± 1.08 to 62.31 ± 1.32 MPa. Moreover, the tensile strength of aramid fibers enhanced slightly. This surface modification strategy is facile to prepare, highly efficient to enhance interface, adaptable to other organic fibers, and meaningful in multifunctional applications. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Influences of dispersion types and area densities of chopped fiber-based interfacial reinforcements on mechanical properties of sandwich structures


Chopped carbon fibers with different dispersion types (colony type and uniform type) and area densities were inserted at sandwich beams, consisting of a PVC foam core covered with two glass fiber/epoxy composite face sheets. The effects of this reinforcement on the interfacial bonding between PVC foam core and glass fiber face sheets were evaluated. Their mechanical properties were measured by three-point-bending and Charpy impact tests. Their structures after mechanical failure were observed by scanning electron microscopy. Compared with the beam without interfacial reinforcement, the bending strength, energy absorption, and impact strength after interfacial reinforcement using 20 g/m2 uniform chopped fibers increased by up to 109%, 184%, and 47%, respectively, surpassing those of other chopped fiber mats. The weight percentage of carbon fibers/sandwich structure was less than 1%, so the chopped carbon fiber interleave had both cost effectiveness and outstanding structural performance. The improvement of interlayer toughness can mainly be attributed to the fiber bridging structure and the interlayer strength. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Regulating polycrystalline behavior of the β-nucleated isotactic polypropylene/graphene oxide composites by melt memory effect


Balancing the stiffness and toughness is always the goal of high performance general plastics, especially for isotactic polypropylene/graphene oxide (iPP/GO) composites. However, during the crystallization of β-nucleated iPP, GO exhibits an α-nucleating effect, and its nucleation efficiency (NE) is higher than that of some conventional β-nucleating agents (β-NAs), thus reducing the formation of β-phase and therefore the toughness of the material. In this article, we used the melt memory effect of β-nucleated iPP/GO composites to improve the formation of β-phase. By adjusting the fusion temperature Tf of β-nucleated iPP/GO composites, the amount of ordered structure in composites was controlled. The crystallization behavior and melting behavior of composites were investigated by differential scanning calorimetry (DSC) and wide-angle X-ray scattering. The results showed that when Tf = 200°C, no ordered structures survived in the melt, no β-phase formed due to the strong α-nucleating effect of GO; in the Tf range of 178–168°C, large amount of β-phase survived in the composites, which helped to improve the formation of β-phase during the subsequent cooling process, and the relative content of β-phase even reached the maximum value of 85.8%. The mechanism of melt structure on the polymorphic behavior of the composites were also investigated, and it was found that the ordered structure in the melt evidently enhanced the NE of β-crystallization, and overcome the challenge from the α-nucleation effect of GO. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

The effect of nonlinear temperature distribution on the vibrational behavior of a size-dependent FG laminated rectangular plates undergoing prescribed overall motion


In this article, the effect of the nonlinear temperature distribution on the free vibration analysis of size-dependent rotating laminated rectangular FG micro-/nanoplates are developed based on modified couple stress theory and exponential shear deformation theory. The modified couple stress theory model contains one length scale parameter to consider the small size effect. In exponential shear deformation theory, exponential functions are used in terms of thickness coordinate to include the effect of transverse shear deformation and rotary inertia. The temperature is assumed to be constant in the plane of the plate and to vary in the thickness direction only. Material properties are assumed to be temperature dependent, and vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The Eigen frequency equation is obtained by the use of Rayleigh–Ritz method. Displacement components are expressed in simple algebraic polynomial forms which can handle any sets of boundary conditions. The effect of material compositions, rotation speed, hub ratio, length-to-thickness ratio, aspect ratio, material length scale parameter, number of layered, and temperature filed on the vibration characteristics is examined. The present theoretical results are verified by comparing with those in literature. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Particle reinforced composites from acrylamide modified blend of styrene-butadiene and natural rubber


Blends of styrene-butadiene rubber and natural rubber that provide balanced properties were modified with acrylamide and reinforced with hydrophilic particles. The rubber composites show improved mechanical properties. Both modified rubber and composites showed a faster curing rate. The crosslinking density of the modified rubber composites increases with increasing amount of acrylamide in the modification. The glass transition temperature of the modified rubber composite shifts to a higher temperature compared with the unmodified rubber composite. The reinforcement factors show that the relative contributions of crosslinking effect and the filler–rubber interaction to the storage modulus vary with temperature. The modified rubber has improved tensile strength, elongation and moduli. The moduli of the modified composite increases and elongation decreases with increasing amount of acrylamide. Tensile fractural surfaces show good adhesion between filler and rubber matrix for all composites. The poly(acrylamide) grafts of the modified rubber increase stress relaxation rate. Stress relaxation also shows a stronger interaction within the modified rubber composites. POLYM. COMPOS., 2018. Published 2018. This article is a U.S. Government work and is in the public domain in the USA

Effects of corona treatment on morphology and properties of carbon based fillers/epoxy nanocomposites


Corona discharge treatment was applied to modify the surface of multi-walled carbon nanotubes and carbon fibers. Successful functionalization was evaluated by ATR-FTIR. Then, the neat and modified fillers were introduced into the epoxy matrix and nanocomposites containing different amounts of filler were obtained. The properties of neat epoxy and nanocomposites including morphology, thermal, mechanics, viscoelastic, and conductivity were evaluated. According to the results, it was found that the corona modification of fillers resulted in breaking of fillers agglomerates and improved their dispersion. The mechanical properties and thermal stability of modified samples were improved with respect to unmodified ones. To analyze the relationship between the interfacial interactions in the nanocomposites and tensile performance, a theoretical model germane to the mechanical behaviors of the nanocomposite was applied. It was found that strong interfacial interactions existed in the modified nanocomposites comparing the unmodified counterparts. Although the electrical conductivity of hybrid filler systems was increased, their tensile properties were reduced compared to CNTs/epoxy nanocomposites. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Fabrication and characterization of antimicrobial starch-based nanocomposite films and modeling the process parameters via the RSM


The main aim of this study is the design and fabrication of degradable nanocomposite films composed of starch/gelatin (S/G)/SiO2 suitable for food packaging applications. Response surface methodology (RSM) was applied to design the fabrication process and to investigate the effect of S/G weight ratio and SiO2 weight percent (wt.%) on the mechanical and barrier properties of the prepared samples. The results revealed that tensile strength and modulus were increased with increasing S/G wt. ratio and introducing SiO2 into the polymer matrix, while elongation at break and water vapor permeability (VWP) decreased. The process optimization was done and various properties of the optimized films such as morphological properties, thermal properties, VWP, degradability, and antibacterial properties were investigated. It was found that the thermal stability of the optimized sample as well as its barrier property against water vapor were improved dramatically as SiO2 presented into the matrix due to proper dispersion and interaction of nanoparticles with the polymer matrix as also confirmed via scanning electron microscopy images. Furthermore, SiO2 has brought significant antibacterial properties for the S/G matrix that is a notable feature for food packaging films. Overall, the results of the current study confirm the S/G/SiO2 compounding could be proper candidate for fabrication of antibacterial degradable food packaging films. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

TiO2/Halloysite hybrid filler reinforced epoxy nanocomposites


TiO2 nanoparticles and Halloysite nanotubes were used together to modify epoxy matrix. They were introduced into the matrix using two different approaches: (a) both TiO2 nanoparticles and Halloysite nanotubes were incorporated into epoxy in their original form; (b) TiO2/Halloysite hybrid prepared by hydrothermal reaction, was incorporated into epoxy. Morphological studies of the nanocomposites were carried out using atomic force microscopy, scanning electron microscopy, and transmission electron microscopy. Tensile and nanoindetation studies were carried out to evaluate the mechanical performance of the nanocomposites. Finally, the dynamic mechanical analysis and thermal degradation properties of the nanocomposites were evaluated. It was found that, the nano-structures of HNT surrounded with TiO2 nanotubes in TiO2/Halloysite hybrid filler eliminated the unfavorable agglomeration of TiO2 nanoparticles in the epoxy matrix and thereby avoiding the deterioration of mechanical properties. However, the hybrid nanostructure in the ternary nanocomposites did not have an evident effect on the glass transition temperature and thermal stability of epoxy matrix. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Synergistic effects of graphene nanoplatelets in thermally conductive synthetic graphite filled polypropylene composite


Polypropylene (PP) was filled with synthetic graphite (SG) and graphene nanoplatelets (G) at different weight fractions. Composites were prepared by the melt mixing process by using a co-rotating twin screw extruder. Mechanical tests were carried out to determine tensile and flexural properties of composites. Dynamic Mechanical Analysis of composites was performed to determine their thermo-mechanical properties, such as storage modulus and loss modulus. Scanning Electron Microscopy was used to observe the fracture surfaces of the composites after tensile tests. The effect of SG and G on thermal properties such as melting and crystallization temperature, thermal conductivity, thermal stability, and coefficient of thermal expansion of PP was investigated. Tensile strength and flexural strength of PP increased with the addition of 10 wt% SG. The highest thermal conductivity achieved in this study at 50 wt% SG and 3 wt% G loading was 4.6 W/mK. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Structure and stability analysis of biocompatible hydroxyapatite reinforced chitosan nanocomposite


Nano-hydroxyapatite has been used in multifunctional potential clinical applications where certain particle size distribution and morphology are required. The hydroxyapatite/chitosan composites were prepared using in situ co-precipitation technique, influence of the reaction temperature on the crystallization and particle growth of the synthesized nano-hydroxyapatite were examined. It was observed that the increase in synthesis temperature had a great influence on particle size and crystal structure of nano-hydroxyapatite, whereas, the low temperature showed inhabitation of the hydroxyapatite growth in c-direction and low crystallinity which was confirmed using XRD and electron diffraction pattern of TEM micrographs. The molar ratio of the bone-like apatite layer for composite prepared at 70°C was higher was higher than the composites prepared at lower temperatures (40°C and −5°C). The AFM images of −5°C, 40°C, and 70°C n-HAp/CTS composite display presence of CTS rich domains. These CTS rich and domains are made of smaller globular shaped particles in which, n-HAp particles are embedded in the polymer matrix. The SBF degraded AFM surface topography of the composites shows the CTS is degraded fast rather the n-HAp. The elastic modulus determined from nanoindentation of −5°C, 40°C, and 70°C n-HAp/CTS composites are 17.91, 24.56, and 30.62 GPa respectively. Hardness values of the three composites in the same order were found to be 0.86, 1.35, and 1.74 GPa, respectively. Macro-mechanical tests showed significant enhancement in elastic modulus, coefficient of friction and hardness of 70°C n-HAp/CTS composites over −5°C and 40°C n-HAp/CTS. However, the SBF degraded samples also performed moderate improvement in nanomechanical property. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Preparation and characterization of graphene oxide and it application as a reinforcement in polypropylene composites


In this article, graphene oxide (GO) is modified using Phosphorous acid via the strong –P = O in the study reported in the paper. And the chemical structure was characterized by Fourier Transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction. And polypropylene (PP) composites are prepared by melt compounding method, and functionalized graphene oxide (FGO) is in situ thermally reduced during the processing. The thermal stability, mechanical and flame properties, and morphology for the char layer of composite materials were separately investigated using TG (Thermogravimetric analysis), tensile and charpy impact tests and SEM (scanning electron microscope). The results of SEM and TEM indicate that FGO nanosheets are homogeneously dispersed in polymer matrix with intercalation and exfoliation microstructure. The FGO/PP nanocomposite exhibits higher thermal stability and flame retardant property than those of the GO counterpart and pure PP. During the thermal decomposition, The –P = O introduced to improve the flame effect and the yield of the carbon residue was increase. The heat release rate and the escape of volatile degradation products are reduced in the FGO-based nanocomposites. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Synthesis of a new nanocomposite based-on graphene-oxide for selective removal of Pb2+ ions from aqueous solutions


In this study, a new nanocomposite was synthesized based on graphene-oxide (GO) for the selective removal of Pb2+ ions from aqueous solutions. In the first step, the GO was synthesized from graphite. Then amino-telechelic poly (hexamethylenediisocyanate-co-propylene glycol) (THMDI-PG) was synthesized. Finally, The GO was reacted with the THMDI-PG to obtain the final nanocomposite. The prepared nanocomposite was then used as the heavy metal ions adsorbent in Pb2+ and binary ionic metal media and showed a selective behavior toward the Pb2+ ions. The abundant oxygen-containing groups on the surfaces of nanocomposite played an important role in Pb2+ ion adsorption on GO and the adsorption was dependent on pH values and independent of ionic strength. Different analysis such as Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy were carried out to characterize the prepared nanocomposite. Moreover, the effect of various adsorption parameters such as pH, adsorbent dose, adsorption time, temperature, agitation speed, and initial concentration of the ions were investigated and optimized. The obtained results showed an efficient performance of the prepared nanocomposite for the removal of the Pb2+ ions. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineers

Effects of water or alkali solution immersion on the water uptake and physicochemical properties of a pultruded carbon fiber reinforced polyurethane plate


Carbon fiber reinforced polyurethane (CFRPU) composites exhibit a high potential in infrastructure application due to their easy manufacturing and excellent mechanical properties. In the present article, a pultruded CFRPU plate subjected to water or alkaline solution immersion at various temperatures was investigated, and compared with a commonly used epoxy-based CFRP plate, in terms of the water uptake and physicochemical properties. As found, CFRPU plates exhibited excellent resistance to both water and alkaline immersion without noticeable degradation in the mechanical properties. No hydrolysis occurred for CFRPU under both immersion conditions for 1 year at 20–60°C. After 1 year of immersion, the tensile properties of CFRPU kept constant or even were enhanced slightly. On the contrary, the epoxy-based CFRP plate showed a noticeable hydrolysis, and decreased in the tensile properties remarkably, especially in the case of the alkaline immersion. In addition, unlike the bond between carbon fiber and the epoxy, the bond between the carbon fiber and the polyurethane matrix was not affected by the above immersion. Accordingly, CFRPU was considered to be much more durable in the water or alkaline immersion conditions. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Novel high-density polyethylene-niobium pentoxide dielectric materials


This study for the first time reports the processing and properties of high-density polyethylene (HDPE) reinforced with niobium pentoxide (Nb2O5) up to 40 wt%. In this work, Nb2O5 was chosen as reinforcement because of its advantageous properties such as good dielectric properties, high temperature stability and excellent biocompatible properties. Almost fully dense HDPE–Nb2O5 composites were prepared via hot pressing route. Both the hardness and dielectric properties of the HDPE increased significantly with the addition of Nb2O5. The hardness of HDPE increased from ∼37 to 60 MPa (i.e., by 62%) with the addition of 40 wt% Nb2O5. The dielectric constant and dissipation factor (dielectric loss) were found to increase with the increasing Nb2O5 content. We have achieved highest ever reported dielectric constant (ε') of 14.66 for HDPE–40 wt% Nb2O5 and the dielectric constant of HDPE is enhanced by 237% and shows the potential of Nb2O5 in improving the dielectric and hardness properties of HDPE. With increasing frequency there was slight decrease in the dielectric constant of HDPE–Nb2O5 composites, whereas not much change in the dielectric constant of pure HDPE. The dielectric constant (ε') of HDPE is 4.6 at 1 MHz, while the ε' value for the composite with 40 wt% Nb2O5 ceramic filler was found to be 13.2. The dielectric loss for the HDPE composites is higher than the neat polymer, particularly HDPE–40 wt% Nb2O5 composite measured with maximum dielectric loss (0.08) at 100 Hz. Nevertheless, the dielectric loss of HDPE materials significantly decreased with further increasing the frequency to 1 kHz and the dielectric loss even significantly lowered with increasing frequency to 1 MHz. The experimental values of dielectric constant show much better values than the calculated values based on theoretical models. The newly developed HDPE–Nb2O5 composites are showing much better dielectric properties than the reported literature values of HDPE materials. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers

Issue Information


Effect of plasma treatment on mechanical and thermal properties of marble powder/epoxy composites


The aim of this work was to study the effect of the plasma treatment on the behavior of composite structures reinforced with marble powder, obtained as processing waste in the “Custonaci” basin. Moreover, different filler amounts (i.e., 10%wt, 20%, 30% in weight) were investigated. For the mechanical characterization, tensile and flexural quasi-static tests, Charpy impact test, and dynamic mechanical thermal analysis (DMTA) were performed. For the thermal stability, thermogravimetric analysis was carried out. Finally, real density and fraction of voids were measured. It was observed that untreated marble powder, on one hand, increases tensile and flexural stiffness and improves thermal stability, on the other hand, introduces a defectivity that produces a decrease of some properties (i.e., ultimate tensile and flexural strength). The plasma treatment induces improvements in all the mechanical properties (i.e., quasi-static and dynamic). Vice versa, the thermal behavior is not affected by the treatment. POLYM. COMPOS., 39:309–317, 2018. © 2016 Society of Plastics Engineers

The effects of carbon nanofiber on the mechanical properties of glass/coir fiber reinforced polyester hybrid composites


Glass and coir fiber hybrid composites were characterized for the addition of 0.1, 0.5, and 1 wt% functionalized fCNFs produced from waste coal fly-ash and were used also as secondary reinforcements for producing both glass and coir fiber composites. Before choosing the hybrid composites fabrication parameters, an optimum fiber mass fraction of glass and coir fibers were obtained by fabricating and mechanically testing the composites specimens with mass fraction of 24, 32, and 40 wt% for glass and 10, 15, and 20 wt% for coir fibers, respectively. From the test results, the glass fiber composites with 32 wt% and coir fiber composites with 15 wt% were found to be the most suitable mass fraction for fabricating the hybrid composites. Based on the functionalization results, the surface-treated CNFs for 6 hr in an acid solution were the best secondary reinforcement in fabricating glass and coir fiber hybrid composites. The hybrid composites testing results showed that both glass and coir fiber hybrid composites reinforced with 0.5 wt% functionalized CNFs were better than those of 0.1 and 1 wt% of CNFs. At higher weight fraction of 1 wt% CNFs, agglomerations could not be prevented and this led to poor mechanical properties. It could also be concluded that the functionalization of these CNFs improved their dispersion within the matrix and resulted in better mechanical properties. One of the future recommendations is that the researchers must focus on utilizing the waste products for producing carbon nanoparticles which could further be used for manufacturing hybrid composites. POLYM. COMPOS., 39:318–328, 2018. © 2016 Society of Plastics Engineers

The synergistic flame-retardant behaviors of pentaerythritol phosphate and expandable graphite in rigid polyurethane foams


The flame-retardant rigid polyurethane foams (RPUFs) containing pentaerythritol phosphate (PEPA) and expandable graphite (EG) were prepared by box-foaming. The flame retardancy of RPUFs was characterized using the limiting oxygen index (LOI) and cone calorimeter. The results show that the PEPA/EG system can effectively enhance the LOI values and reduce the peak release rate of RPUFs comparing with the foams only containing PEPA or EG although the flame retardants in all the samples are same proportion. The two results imply that the PEPA/EG system form flame-retardant synergistic effect. The micromorphology and chemical structure of residues of RPUFs were also investigated by scanning electron microscope and Fourier transform-infrared instruments. During combustion, the polyphosphates and their related analogues generated by PEPA can combine with the surfaces of expanded graphite, thereby resulting in the formation of the improved char layer. The layer possessed increased barrier effect and thereby imposing the better flame retardancy to RPUFs. POLYM. COMPOS., 39:329–336, 2018. © 2016 Society of Plastics Engineers

Manufacturing and characterization of braidtruded fiber reinforced polymer rebar


Fiber reinforced polymer (FRP) rebar can serve as a noncorrosive alternative to conventional steel rebar for use in concrete reinforcement. By combining pultrusion and braiding into a single manufacturing process called braidtrusion, FRP rebar consisting of both unidirectional and off-axis fibers can be produced. In this study, a variation on the braidtrusion process was introduced, utilizing an impregnation ring and dieless curing system to produce high quality FRP rebar in a continuous manner. The resulting rebar was characterized to assess the quality and consistency of the manufacturing process. Degree of cure, braid angle, cross-sectional area, and fiber volume fractions were measured, and a general examination of the rebar microstructure was conducted. In addition, analytical equations based on previous works were presented to predict braid angle and cross-sectional area of the resulting rebar based on manufacturing parameters. The predictions made using these equations were found to be in good agreement with the experimental results, and can be used to facilitate future design and manufacturing of FRP rebar. POLYM. COMPOS., 39:337–350, 2018. © 2016 Society of Plastics Engineers

Electrorheological, viscoelastic, and creep-recovery behaviors of covalently bonded nanocube-TiO2/Poly(3-octylthiophene) colloidal dispersions


In this study, nanocube-TiO2 and covalently bonded nanocube-TiO2/poly(3-octylthiophene), (P3OT) core/shell structured hybrid nano materials were dispersed in silicone oil (SO) and antisedimentation stabilities of these suspended particles were determined to be 31% and 65%, respectively. Polarizabilities (Δεnanocube-TiO2 = 0.1925 and Δεnanocube-TiO2/P3OT = 0.0920) and relaxation times (λnanocube-TiO2 = 3.4 × 10−4 s and λnanocube-TiO2/P3OT = 2.7 × 10−4 s) of dispersions were determined by dielectric measurements. Optical microscopy studies showed that these suspensions were highly polarizable under externally applied electric field strengths and classified as electrorheological (ER) active materials. The effects of volume fraction of dispersed phase, shear rate, shear stress, external electrical field strength, frequency, and temperature onto ER activities of these suspensions were studied. Yield stresses of nanocube-TiO2 and nanocube-TiO2/P3OT were determined to be 128 and 310 Pa, respectively. Viscoelastic studies revealed that the elastic characters of the particles were dominant to their viscous ones and elasticity moduli were determined to be 31.5 and 142 kPa, for nanocube-TiO2 and nanocube-TiO2/P3OT, respectively. Finally, the creep-recovery behaviors of these suspensions were identified and %recoveries of nanocube-TiO2/SO and nanocube-TiO2/P3OT/SO systems were determined to be 39% and 73%, respectively under τ = 5 Pa external shear stress. Because of the high polarizabilitiy, ER activity, vibration damping, and creep-recovery properties, the nanocube-TiO2/P3OT/SO suspension system was classified as smart material and suitable for potential vibration damping applications. POLYM. COMPOS., 39:351–359, 2018. © 2016 Society of Plastics Engineers

Determination of the unsaturated through-thickness permeability of fibrous preforms based on flow front detection by ultrasound


The permeability of fibrous preforms used as reinforcements for fiber-reinforced polymeric composites is a decisive parameter for simulation-based predictions of common defects that occur during the filling process. This study focuses on the transverse permeability which becomes important for high thickness parts. An instrument that detects the transverse flow front by ultrasound and determines the transverse permeability has been developed. In contrast to other approaches, the developed permeameter uses a nondeflecting (metallic) tool while the selected sensing method is nonintrusive to the material. Novel electromechanical features allow a wide range of measurable preforms. The remaining limitations of the system have been identified and the model that correlates raw ultrasound measurements with flow front has been verified by visual observations. The transverse permeabilities of 18 different preforms have been determined in an experimental scheme designed to isolate the influence of preform thickness. POLYM. COMPOS., 39:360–367, 2018. © 2016 Society of Plastics Engineers

Synthesis and property evaluation of a novel polyacrylamide-montmorillonite composite for water shutoff and profile control in high salinity reservoirs


Polyacrylamide-montmorillonite organic-inorganic composites (poly[AM/O-MMT]) were synthesized by copolymerization of acrylamide (AM) on organic modified montmorillonite (O-MMT) using N,N-methylene-bis-acrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator in an aqueous solution. The montmorillonite (MMT) was modified by methacryloyloxy ethyl dimethyl hexadecyl ammonium bromide (DMB) which was synthesized by 2-(dimethylamino) ethyl methacrylate with 1-bromohexadecane. The FTIR and XRD were used to verify the organification of MMT with DMB. The effects of the amount of the DMB and O-MMT on water absorption were studied. The swelling behavior in different saline solution and re-swelling ability in distilled water were investigated. The results showed that DMB and O-MMT content have an important effect on the water absorption of the composites. The addition of the DMB enhanced the salt resistance and delayed the swelling speed of the poly(AM/O-MMT). Simultaneously, the toughness was measured. The water blocking and profile control ability were evaluated by core physical simulation experiments. The results indicated that the poly(AM/O-MMT) has good plugging ability and profile control ability. The properties tested indicated that the poly(AM/O-MMT) has a promising prospect to be applied as a profile control or water shut-off agent for enhanced oil recovery in high salinity reservoirs. POLYM. COMPOS., 39:368–376, 2018. © 2016 Society of Plastics Engineers

Study on the dispersion of carbon black/silica in SBR/BR composites and its properties by adding epoxidized natural rubber as a compatilizer


This paper studied the influence on the properties of SBR/BR composites filled with carbon black (CB) and silica via adding epoxidized natural rubber (ENR-25) as a compatilizer. Payne effect, morphology, crosslink density, mechanical, and dynamic properties were studied. The results showed Payne effect receded by adding ENR-25 to SBR/BR/CB/silica composites and the aggregation of CB and silica both weakened as well. Thus, tear strength and modulus were improved significantly, also the crosslink density and bond rubber content Dynamic Mechanical Analyzer (DMA) data indicated the tanδ value at 0°C and 60°C increased when CB was replaced by silica. Meanwhile, the value at 0°C exhibited a greater improvement than that at 60°C when adding ENR-25, which means an excellent wet traction performance. The abrasion loss and aging resistance presented well with ENR-25 as a compatilizer, but no improvement on the heat build-up performance. POLYM. COMPOS., 39:377–385, 2018. © 2016 Society of Plastics Engineers

Biodegradation properties of melt processed PBS/chitosan bio-nanocomposites with silica, silicate, and thermally reduced graphene


Melt processed bio-nanocomposites of poly(butylene succinate) (PBS)-chitosan (CS) generated with varying amounts of silica, alumina-silicate, and thermally reduced graphene were analyzed for their biodegradation behavior. The nanocomposite samples were embedded in soil under natural environment for varying periods of time and the weight loss analysis was complemented with changes in surface morphology, crystallinity, and thermal degradation. Both the type and amount of filler were observed to affect the extent of biodegradation, though no change in biodegradation mechanism occurred. Nanocomposites had in general lower extent of weight loss than the pure blend, but the extensive surface roughness and cracks were observed for all systems indicating the initiation of biodegradation. Silica and silicate nanocomposites exhibited higher extent of biodegradation in comparison with graphene nanocomposites possibly because of the obstructive pathways to microbes in the presence of high aspect ratio graphene platelets. The crystallinity in the pure blend and nanocomposites was observed to increase as a function of embedding time because of degradation of the random amorphous material in the initial degradation phase. Subsequently, the increase levelled off because of attack of microbes on more organized crystalline content, which was also supported by the reduction in overall weight loss. Increase in melting point of PBS with embedding time as well as depletion of CS flakes from the cross-section of the composites in AFM confirmed that CS was degraded earlier than PBS. Thermal analysis also indicated faster onset of degradation of CS with soil burial time. The degradation studied through TGA-MS also revealed that degradation was accompanied by evolution of H2O, CO2, and NH3, along with other components. The temperature of evolution of these components from the nanocomposites was also affected during different stages of biodegradation. POLYM. COMPOS., 39:386–397, 2018. © 2016 Society of Plastics Engineers

Impact and flexural properties of PP/CaSiO3 composites


The effects of filler surface treatment and content on the impact fracture toughness and flexural properties of polypropylene (PP) composites filled with wollastonite (CaSiO3) were investigated. The results showed that the introduction of the filler could toughen and reinforce the PP; the influences of the filler surface treatment on the toughness and strength were significant; the values of the Izod V-notched impact strength and the Charpy V-notched impact strength of the composites increased with increasing the filler weight fractions; the values of flexural modulus increased with increasing the filler weight fractions; the flexural strength increased when the filler weight fraction was lower than 10% and then varied slightly. This toughening effect should be attributed to the stress concentration because of strip shape of the filler and to block the development of the notched cracks in the matrix, improving the notched sensitivity to the impact fracture of the PP composites. This study should be helpful to understand the mechanisms of CaSiO3 reinforcing and toughening PP resin. POLYM. COMPOS., 39:398–404, 2018. © 2016 Society of Plastics Engineers

Enhanced mechanical and thermal properties of short carbon fiber reinforced polypropylene composites by graphene oxide


The article reports the mechanical and thermal properties of graphene oxide (GO)/short carbon fiber (SCF)/polypropylene (PP) composite. The GO-coated SCF (GO-SCF) was prepared by a simple physical absorption method. The GO filled PP (GO-PP) was obtained by extrusion melt-mixing method. Then, GO-SCF reinforced GO-PP composite (GO-SCF/GO-PP) was prepared via the conventional extrusion compounding and injection molding techniques. The tensile, flexural and impact strengths of GO-SCF/GO-PP were obviously improved due to the chemical reaction and mechanical interlocking between the GO on SCF surface and PP. X-ray diffraction results showed the GO on SCF surface could act as a β-nucleating agent for PP crystallization. Differentials scanning calorimeter showed that GO-SCF/GO-PP had good thermal stability. Therefore, the multiscale and synergistic effects of GO-SCF/GO-PP show the extensive potential on improving mechanical and thermal performance for various fields. POLYM. COMPOS., 39:405–413, 2018. © 2016 Society of Plastics Engineers

A comparative study of rice husk ash and siliceous earth as reinforcing fillers in epoxidized natural rubber composites


Rice husk ash (RHA) and siliceous earth (SE) were compared as alternative reinforcing fillers in epoxidized natural rubber (ENR) vulcanizates. The effects of RHA and SE on processability, curing characteristics, mechanical, thermal and morphological properties, and thermoelastic behavior of vulcanizates were studied, in the presence and absence of bis(triethoxysilylpropyl) tetrasulfide (TESPT) silane coupling agent. The results indicated that the RHA offers processing advantages over the commercial SE. The filled ENR vulcanizates without TESPT provided higher tensile strengths than the unfilled ENR vulcanizates, but had lower elongations at break. This is attributed to physical interactions between filler particles and rubber matrix, which affects the reinforcement by the filler. The modification of filler surfaces with TESPT resulted in further improved properties of the rubber vulcanizates. This is attributed to the coupling of polymer matrix and filler particles via TESPT linkages that increased the polymer–filler interactions. It was also found that the RHA filler, a renewable resource, exhibited similar reinforcement to the conventional SE. This indicates that the RHA has great potential as a reinforcing filler that can substitute for conventional SE in polymer composites. POLYM. COMPOS., 39:414–426, 2018. © 2016 Society of Plastics Engineers

The functional features and interface design of wood/polypropylene composites based on microencapsulated wood particles via adopting in situ emulsion polymerization


The interface design based on microencapsulated wood particle in wood-polypropylene-composites (WPCs) was reported via in situ emulsion polymerization of butyl-acrylate (BA)/methyl methacrylate (MMA). SEM images, FTIR spectra, and surface parameters proved microencapsulation efficiently. With compatible-crosslinking network on wood surface, wood polypropylene composite was reinforced. For hydrophobic interface, by soaking for 72 h, water absorbance of wood–polypropylene composite decreased from 16.7 to 0.17 wt%. As well as flexural strength and tough parameters, tensile strength reached 37.39 MPa which was enhanced by about 83%. Viscoelastic properties showed microencapsulated effect enhanced the storage modulus of composites and the glass-transition temperature (Tg) of polymer components. Ascribing to microencapsulated crosslinking interactions and weak chain-motions, the melting enthalpy and initial decomposition temperature (Td) of wood–polypropylene composite were also improved. To wood (adopting 72.9 wt% rigid MMA)-polypropylene composite, initial Td was improved from 248 to 356°C. POLYM. COMPOS., 39:427–436, 2018. © 2016 Society of Plastics Engineers

Temperature effects in end milling carbon fiber reinforced polymer composites


The temperatures at the cutting area rise excessively in machining of CFRP due to the low thermal conductivity of the material. And machining damages become aggravated with cutting-area temperatures approaching to the glass transition temperature of resin matrix. Therefore, controlling the cutting-area temperature at the suitable range is remarkably important for improving machining qualities. This article presented experimental investigations into cutting-area temperature influences on cutting force, surface integrity, as well as subsurface quality in end milling of multi-directional CFRP composites, and further discussed cutting mechanism variations. The cutting-area temperatures were controlled under three ranges by employing pressured cryogenic nitrogen gas and no coolants. The machining quality under low temperature in general was better than that under high temperature. Particularly, morphologies under high temperatures indicated fibers were bended to fracture resulting in severe subsurface damages. In contrast, the hardened matrix at low temperatures offered fibers better support, and the composites were easily squeezed to rupture which led to superior cutting performance. However, as the temperature reached extremely low, the cutting force increased dramatically and then could reduce tool life. Thus the suitable temperature range is proposed for the first time in machining CFRP. POLYM. COMPOS., 39:437–447, 2018. © 2016 Society of Plastics Engineers

Preparation of nacrite nanorolls and their reinforcing effect in LLDPE matrix


Nacrite nanorolls were prepared by the delamination and rolling of the platy nacrite particles and the nacrite nanorolls were melt-compounded with LLDPE to prepare a novel Nacrite/LLDPE composite. In this method, hexylamine was intercalated into the interlayer space of methoxy-modified nacrite precursor and the deintercalation of nacrite-hexylamine intercalation complex in toluene resulted in the delamination and rolling of nacrite layers. The nacrite nanorolls were composed with linear low-density polyethylene (LLDPE) to prepare a novel Nacrite/LLDPE composite. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption–desorption test were used to evaluate the prepared nacrite nanorolls. The results showed that the interlayer octahedral surface of nacrite was grafted with methanol and the methoxy-modified nacrite was intercalated with hexylamine. The deintercalation of nacrite-hexylamine intercalation complex in toluene disturbed the orderly arrangement of nacrite layers, leading to a delamination of the layered particles and subsequent formation of aluminosilicate nanorolls. The specific surface area (SSA) and Vpor value of nacrite nanorolls reached 34.69 m2/g and 0.22 cm3/g (4.52 m2/g and 0.13 cm3/g for raw nacrite). Furthermore, the mechanical properties test confirmed that the introduction of nacrite nanorolls into LLDPE matrix could improve the tensile and tear strength. 6.4% and 6.8% higher tensile strength than the pure LLDPE were observed for Nacrite/LLDPE composite with 2 wt% and 4 wt% nacrite nanorolls filler. POLYM. COMPOS., 39:448–456, 2018. © 2016 Society of Plastics Engineers

Experimental investigation on air void and compressive strength optimization of resin mineral composite for precision machine tool


Resin mineral composite (RMC) consists of epoxy resin, granite aggregate and fly ash, and which can be used to produce precision machine tool beds due to its superior vibration alleviating properties. However, applications of RMC are restricted due to its limited mechanical strength. In this paper, the effects of the air void on the compressive strength of RMC were firstly introduced. Then the effects of vibration time, initial temperature of resin, mass of compression mould, vacuum degree, number of layers and mass content of defoamer on the air void and compressive strength of RMC were thoroughly investigated. Experimental results show that the air void (compressive strength) of RMC first decreases (increases) and then stabilizes as the vibration time and number of layers increases. Results also show that the air void (compressive strength) of RMC first decreases (increases) and then increases (decreases) as the initial temperature of resin, mass of compression mould, vacuum degree and mass content of defoamer increases. In order to further reduce the air void of RMC and increase the compressive strength of RMC, five different compound technologies (i.e., CTA, CTB, CTC, CTD, CTE) at different temperature (10°C and 40°C) were investigated. The optimum air void (compressive strength) of RMC was achieved by the CTE at 10°C, in which the air void (compressive strength) decreased (increased) by 44.4% (19.7%) compared to the RMC poured by CTA (standard pouring technologies) at 10°C. Afterwards, the relationship between air void and compressive strength of RMC was studied systematically. POLYM. COMPOS., 39:457–466, 2018. © 2016 Society of Plastics Engineers

Hybridization effects on charpy impact behavior of basalt/aramid fiber reinforced hybrid composite laminates


Basalt/aramid hybrid fiber reinforced composite laminates were prepared to examine the effect of hybridization on Charpy impact behavior of aramid fiber reinforced composite laminates. The effect of position of basalt layers on the impact behaviors was also investigated by preparing hybrid composite laminates with the substitution of basalt layers into different positions. The position change of basalt layers in the hybrid configurations were resulted in variations in the impact behavior. The impact energy and impact damages strictly depended on impact behavior of fiber at impacted surface due to the difference between deformation characteristics of basalt fiber and aramid fiber. When the basalt layer was at the impacted surface, the hybrid composite laminates exhibited a lower impact energy. This was attributed to the restriction in deformation of aramid layers. The position of basalt layers resulted in variations in the impact behavior of hybrid composite laminates. POLYM. COMPOS., 39:467–475, 2018. © 2016 Society of Plastics Engineers

Thermosetting composites prepared using husk of pine nuts from Araucaria angustifolia


The high consumption of pine nuts as food leads to high amounts of husk dispensed as waste. The incorporation of the husk from pine nut into composites appears as a strategic route to explore the commercialization of the Araucaria angustifolia. The present study aims to prepare and characterize thermosetting composites of urea and phenol formaldehyde and husk of pine nuts. For this, husk particles, paraffin emulsion, ammonium sulfate, and resins, were mixed with a high-shear mixer and then cured by flat-pressing at 4 MPa, 120°C, for 5 min. SEM and optical images revealed good homogenization between resin and husk. DTG and DSC results showed chemical affinity between filler and matrix—tracked by shifts in the DTG peaks of the husk. The UF composites showed higher wettability and water absorption; therefore higher thickness swelling. The UF and PF composites with 30% of resin provided the greatest repellency to water, and the highest mechanical properties. It was possible to prepare composites of UF and PF resins loaded with 70% and 80% of husk from pine nuts. POLYM. COMPOS., 39:476–483, 2018. © 2016 Society of Plastics Engineers

Fabrication and characterization of isolated lignin as adhesive for three-ply plywood


In order to reduce the emission of formaldehyde of plywood and improve the utilization of lignin, isolated lignin was successfully prepared from wood chips with polyethylene glycol (PEG) 400 at the various weight ratios. The characterization was determined with thermogravimetry, Fourier transform infrared spectroscopy, 13C-nuclear magnetic resonance analysis, and dynamic viscosity measurement. The results showed that more PEG moiety were grafted at alpha carbon position of lignin structure on increasing the weight ratio, resulting in the poorer thermostability and more formation of hydrogen bonding. Isolated lignin prepared with weight ratio of 1:4 exhibited the best dynamic viscosity property among all, and the lignin-based three-ply plywood which meets the shear strength requirement for type II plywood according to GB/T17657-2013 were fabricated. Accordingly, isolated lignin with PEG-400 could be considered as a promising adhesive for preparation of formaldehyde-free plywood. POLYM. COMPOS., 39:484–490, 2018. © 2016 Society of Plastics Engineers

Effects of glass fibers on mechanical and thermal properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)


This study investigates the effects of glass fiber on the mechanical and thermal properties of bacterial polyester, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH). PHBH composites were prepared by melt-compounding and injection molding, using PHBH with 3-hydroxyhexanoate (3HH) molar fractions of 5.6% and 11.1%, and short glass fiber content varying from 0 to 23 volume percent. Tensile test results suggested that the glass fiber addition significantly increased Young's modulus and strength of PHBH. The Halpin–Tsai and Tsai–Pagano equations were used to predict Young's modulus of PHBH composites while the modified Kelly–Tyson model with the Bowyer–Bader method were used for strength prediction. These predictions gave reasonable estimates for the mechanical properties of PHBH composites. Differential scanning calorimetry results suggested that glass fiber addition had little effect on the degree of crystallinity of PHBH, as well as on the crystallization half-time of PHBH containing 5.6 mol% 3HH. POLYM. COMPOS., 39:491–503, 2018. © 2016 Society of Plastics Engineers

Effects of processing steps and hygrothermal ageing on mechanical performance of PA6GF30 composite: Interfacial shear strength


Polyamide 6 reinforced with glass fiber was prepared using extrusion compounding and injection molding processes. The effect of processing steps on the orientation and the fiber length were investigated. Optical observations shows that the fibers are predominantly orientated parallel to the main mold flow direction. In addition, the measurements of fiber length after both extrusion and injection molding reveal a clear shortening effect of these techniques on their length. Such reduction results probably from the fiber–machine, fiber–fiber, and fiber–polymer interactions. Afterwards, mechanical characterizations were performed on samples before and after ageing in distilled water and glycol–water mixture. The mechanical characteristics were then used as input parameters in the Kelly–Tyson model. Subsequently, the evolution of mechanical properties, the fiber/matrix bond strengths and reinforcement efficiency of the studied material were deeply discussed in both states. Results reveal that a full immersion in either distilled water or glycol–water mixture, affects significantly the interfacial fiber/matrix region as obviously confirmed by SEM observations. So, a decrease of the interfacial shear strength value was recorded. Accordingly, the reinforcement efficiency is extremely reduced after hygrothermal ageing leading to an overall fall in mechanical parameters. POLYM. COMPOS., 39:504–512, 2018. © 2016 Society of Plastics Engineers

Properties of polymer composites based on bisphenol A epoxy resins with original/modified steel slag


Recently, many inorganic solid wastes have accumulated as a byproduct in several industries and their storage is one of the major problems. Among these wastes, steel slag has attracted attention to utilize with different purposes. In this study, original steel slag (OS) and modified steel slag (MS) were evaluated as a filler to prepare low-cost epoxy composites. The effect of components on the properties of steel slag/epoxy composites (SECs) was investigated with various analyses and tests. Physicomechanical and thermal properties of the SECs were compared with each other and neat epoxy resin (ER). Good dispersion of OS and MS in the ER matrix was determined with X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM). Tensile strength, Young modulus, and hardness values of the SECs were enhanced after modification of OS. Any change on adhesion and corrosion resistance of the SECs was not observed; however water sorption percent was increased with the addition of components. As per thermogravimetric analyses (TGA) and vicat softening temperature (VST) analyses, SECs cured with anhydride showed higher decomposition temperature than the other hardener. Also, PEG addition slightly decreased thermal stability of the SECs. POLYM. COMPOS., 39:513–521, 2018. © 2016 Society of Plastics Engineers

Synergistic effects of modified hydrotalcite on improving the fire resistance of ethylene vinyl acetate containing intumescent flame retardants


The NH2 SO3−1 intercalated MgAl-LDH (SA-LDH) was prepared and then introduced into ethylene vinyl acetate (EVA) in association with intumescent flame retardants (IFR) in order to improve the flame retardancy of the composite. The structure and thermal stability of SA-LDH was characterized by Fourier transform infrared, X-ray diffraction, transmission electron microscopy, and thermogravimetry analysis. The flame retardancy of EVA composite was evaluated by limiting oxygen index (LOI), vertical burning UL-94, and cone calorimeter tests. The presence of only 1 wt% SA-LDH could increase the LOI of EVA/IFR composite from 24.8 to 26.9, and significantly reduced the peak HRR value. The morphology of char after combustion was observed by scanning electron microscope, and it revealed that the presence of SA-LDH was beneficial to form compact char structure. It was proposed that there existed synergism between SA-LDH and IFR in improving the fire performance of EVA composite. POLYM. COMPOS., 39:522–528, 2018. © 2016 Society of Plastics Engineers

Two series of inorganic melamine salts as flame retardants and smoke suppressants for flexible PVC


Two series of inorganic melamine salts containing a tungstate or molybdate were synthesized as a flame retardant and smoke suppressant for flexible PVC, and their flame retardancy and smoke suppression were studied by limiting oxygen index (LOI), smoke density rating (SDR) test, cone calorimeter, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). It can be found that the presence of melamine tungstate or melamine molybdate causes an obvious increase in LOI and a decrease in SDR. The cone calorimeter results reveal that melamine tungstate or melamine molybdate can clearly change the decomposition behavior of PVC and form a char layer on the surface of the composites, consequently resulting in efficient reduction of the flammability parameters, such as heat release rate, smoke production rate, total smoke production, and so on. The TGA and SEM results demonstrate that melamine tungstate can delay the degradation of PVC and improve the stability of the char residue. Moreover, melamine molybdate and the PVC matrix form a novel intumescent flame retardant and smoke suppression system, in which the PVC matrix acts as the carbonization agent and molybdate as the acid source (Lewis acid). Molybdate can catalyze the dehydrochlorination reaction and promote the crosslinking reaction of PVC effectively. Melamine (MA) and the released hydrogen chloride can act as the blowing agent, which enhance the intumescence of the char. POLYM. COMPOS., 39:529–536, 2018. © 2016 Society of Plastics Engineers

Characteristics and properties of wood/polyaniline electromagnetic shielding composites synthesized via in situ polymerization


Semiconducting wood/polyaniline (PANI) composites were synthesized via in situ polymerization of aniline monomer, which was impregnated into the wood veneer in advance. Thus, the resulting composites exhibited the characteristics of the conducting PANI and natural wood. The light microscopy and scanning electron microscopy images showed that PANI was uniformly dispersed into the wood substrate. The weight percent gain and volume bulk increase of the composites were 16.13% and 6.21%, respectively. The equilibrium water absorption studies showed that the composites were less hydrophilic, because of the addition of hydrophobic PANI. The electrical conductivity of the wood/PANI composite ranged from 2.57 × 10−5 to 9.23 × 10−3 S cm−1 and was tuned by changing the phosphoric acid concentration. The electromagnetic shielding effectiveness of the wood/PANI composites was mainly in the range 30–60 dB, which may be used for general industry or commercial electronics. Fourier transform infrared spectra revealed that PANI was closely polymerized onto the wood substrate and allowed the accessibility of the amine groups of the aniline to the hydroxyl groups of the wood. Furthermore, the X-ray diffraction analysis indicated that the crystal lattice of the crystalline cellulose region was not damaged, and the relative crystallinity of wood increased. POLYM. COMPOS., 39:537–543, 2018. © 2016 Society of Plastics Engineers

Preparation of chitosan nanoparticles as a drug delivery system for perindopril erbumine


Chitosan nanoparticles (CSNPs) and perindopril erbumine (PE)-loaded chitosan nanoparticles (PE-CSNPs) were prepared using the ionic gelation method with tripolyphosphate (TPP) as a crosslinking agent. The XRD pattern of the PE-CSNP nanocomposite shows suppression of the peaks corresponding to crystallized chitosan due to its conversion to the amorphous form after crosslinking and PE loading. The presence of the drug in the nanocomposite was confirmed by a shift in the FTIR transmittance peak from 1,289 to 1,279 cm−1. The mean diameter of the PE-CSNP nanocomposite was 44 nm. Analysis of the ultraviolet spectrum indicated that the loading efficiency and the encapsulation efficiency were 30.5% and 94.1%, respectively. The in vitro drug release profile was also determined by ultraviolet spectroscopy, which showed a sustained release over a period of 2 h (99.8%), starting with initial burst release (40% in 10 min). According to our results, no IC50 (the half maximal inhibitory concentration) against the 3T3 cell line was found for free PF or the PE-CSNP nanocomposite up to 100 μg mL−1. POLYM. COMPOS., 39:544–552, 2018. © 2016 Society of Plastics Engineers

Low-cost poly(vinyl chloride)/poly(α-methylstyrene-acrylonitrile)/chlorinated polyethylene/mineral fillers composites with highly improved thermal conductivity I: Mechanical and thermal performance


Low-cost mineral fillers, including mica, calcium carbonate (CaCO3), and alumina oxide (Al2O3) were used to modify poly(vinyl chloride) (PVC)/α-methylstyrene–acrylonitrile copolymer (α-MSAN)/chlorinated polyethylene (CPE) blend. With the addition of mineral fillers, the thermal conductivity, flexural modulus and overall thermal stability were improved; however, loss in tensile properties, impact and flexural strength, and initial thermal stability accompanied the other improved properties. The theoretical modeling results indicate that mica has a more effective potential to increase the thermal conductivity and better interfacial interaction with the polymeric matrix. Therefore, mica is the best candidate for enhancing the properties of the composites. POLYM. COMPOS., 39:553–559, 2018. © 2016 Society of Plastics Engineers

Improved dispersion of attapulgite in polypropylene by grap oxide and the enhanced mechanical properties


Attapulgite (ATT) is a one-dimensional (1D) nanorod which shows great potential as an effective filler for enhancing polymers. However, natural ATT is hard to develop its nanoscale reinforce advantages because it always tend to aggregate in the matrix. In this work, hybrid filler composed of ATT nanorods attached on two-dimensional (2D) graphene oxide (GO) nanoplatelets was prepared through electrostatic assembly, and then introduced into polypropylene (PP) matrix using melt blending method. A better dispersion of ATT in PP matrix was obtained with the aid of GO nanosheets. The tensile strength, Young's modulus and storage modulus of PP composites were improved simultaneously. Taking GO as an assistant-dispersant is believed to be a novel design strategy and effective approach for developing high performance nanocomposites. POLYM. COMPOS., 39:560–568, 2018. © 2016 Society of Plastics Engineers

Flame retarded polyethylene/wood flour composites with high performances: Satisfying both sides with intumescent flame retardants and synergistic compatibilizers, respectively


WPC is inflammable that threatens the safety of life and property. To reduce the risk of conflagration, it is important to make WPC flame retardant. But the flame retarded WPC is usually highly loaded which deteriorates its mechanical properties. It is difficult to satisfy both sides. In this article, we make attempt to prepare the flame retarded polyethylene/wood flour (WF) composites with high mechanical properties by using an ammonium polyphosphate and phosphorus based intumescent flame retardants (IFR) system. To maintain the high performances of the flame retarded composites, the multi-monomer graft copolymers are synergistically used as the interfacial compatibilizers for the composites. Cone calorimeter testing, UL94 flame tests, limited oxygen index (LOI) and thermogravimetric analysis (TGA) are used to evaluate the flammability properties and thermal stability of the composites. Results show that WF enhances the flame retardancy of the composites with the help of suitable IFR system. The coordination of flame retardants with WF content is an effective measure to control the fire spreading and the risk of combustion. The incorporation of flame retardants transforms the role of WF from the inflammable material into the charring agent of IFR system. By using the IFR system, a highly flame retarded composite with V0 classification based on the vertical combustion testing was successfully prepared. With the help of the synergistic compatibilizers, it is possible to prepare an intumescable flame retarded rPE/WF composites with high performances. The incorporation of WF, and flame retardants can improve the thermal stability of the co[...]

Study on the microstructure evolution of TiO2-reinforced HDPE nanocomposites by synchrotron small angle X-ray scattering


This work studies the effect of titanium dioxide (TiO2) nanoparticles on mechanical properties, thermal behavior and microstructures of high-density polyethylene (HDPE). Differential scanning calorimetry (DSC) results showed that melting temperature and crystallinity of the nanocomposites are affected by incorporating TiO2; the crystallinity reaches maximum at low TiO2 loading following with a significant reduction when the content of TiO2 higher than 2 wt%. To deeply understand structure–property relationship, SAXS experiments were carried out. The results indicated that the nanoparticles were homogeneously distributed in the HDPE matrix. The TiO2 nanoparticles exhibit surface-fractal characteristic at small scale. At large scale, with TiO2 content increasing, TiO2 clusters grow gradually until 2 wt%. The optimum microstructures and mechanical properties of HDPE/TiO2 nanocomposites were achieved at about 2 wt% loading. POLYM. COMPOS., 39:580–587, 2018. © 2016 Society of Plastics Engineers