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Preview: Polymer Composites

Polymer Composites

Wiley Online Library : Polymer Composites

Published: 2017-11-01T00:00:00-05:00


Competition effect of shear-induced nuclei and multiwalled carbon nanotubes (MWCNT) on β-isotactic polypropylene (iPP) formation in preshear injection-molded iPP/MWCNT nanocomposites


In this study, the influence of multiwalled carbon nanotubes (MWCNT) on β-isotactic polypropylene (iPP) formation in preshear injection-molded iPP/MWCNT nanocomposites is investigated layer by layer by wide angle X-ray diffraction (WAXD). WAXD results suggest that in preshear injection-molded pure iPP, β-iPP exists in not only the shear region, but also the core region as a result of preshear-induced nucleation. The addition of MWCNT can inhibit the β-iPP formation. As the depth away from the specimen surface is decreased, the inhibiting effect is decreased. The reason responsible for that is given as follows: (1) with the addition of MWCNT, extra nuclei are induced during preshear. Both MWCNT and extra nuclei serve as α-iPP nucleation point. Therefore, the formation of β-iPP is restricted; (2) the cooling rate gradient is widely accepted to exist in the injection molded sample. A larger cooling rate at a smaller depth will give rise to a lower α-iPP crystallization onset temperature and a lower nucleation efficiency of MWCNT. Since that β-iPP grows only in the temperature range of 105°C-140°C, the inhibiting effect of MWCNT on β-iPP becomes weaker as the depth is decreased. POLYM. COMPOS., 00:000–000, 2017. © 2017 Society of Plastics Engineers

Synthesis and properties of cured epoxy mixed resin systems modified by polyphenylene oxide for production of high-frequency copper clad laminates


Redistributed polyphenylene oxide (rPPO) was synthesized and used to modify epoxy resin for use as high-frequency Copper Clad Laminates (CCLs). The chemical composition, thermal stability and micro morphology of cured rPPO/(Epoxy resin)EP mixed resin systems were analyzed and their mechanical, thermal conductivity and dielectric properties determined. These results revealed that the molecular weight of rPPO containing 20 wt% bisphenol A (BPA) was greatly reduced, with a number-average molecular weight of rPPO as low as 2652.7. Cured rPPO/EP mixed resin systems were prepared with improved heat resistance properties, exhibiting a maximum heat weight loss temperature (Td50%) of 421°C, that was 151°C higher than that observed for pure epoxy resin. Scanning results show that reducing the molecular weight of PPO effectively improves the compatibility with E-51. Broadband dielectric spectrum analysis revealed that the cured rPPO/EP mixed resin systems had a lower dielectric constant (3.76/107 Hz) and a smaller dielectric loss of 2.11 × 10−3/107 Hz than pure epoxy resin. Similarly, composite laminates derived from cured rPPO/EP mixed resin also showed a lower dielectric constant (4.65/107 Hz) and dielectric loss (6.25 × 10−4/107 Hz) than laminates derived from pure epoxy resin. POLYM. COMPOS., 00:000–000, 2017. © 2017 Society of Plastics Engineers

Electrospun functionalized magnetic polyamide 6 composite nanofiber: Fabrication and stabilization


One of the major challenges in the preparation of magnetic nanoparticles is to minimize the aggregation of the obtained nanoparticles. In addition, the presence of functional groups on the surface of the magnetic nanoparticles and the allowance of further functionalizing of these particles with drugs and therapeutic agents are other drawbacks. Functionalized magnetic polyamide 6 composite nanofibers (magnetic PA6) with diameters of 120 and 200 nm were fabricated by electrospinning process. The surface of the magnetic particles was functionalized with polyethylenimine (PEI), 3-aminopropyltriethoxysilane (APTS), polyethylene glycol, and tetraethoxysilane on an individual basis. The dispersion of magnetic nanoparticles within the polymeric solution of polyamide 6 was created and examined by the electrospinning process. The morphologies and diameter distributions of the resultant nanofibers were investigated by scanning electron microscopy (SEM). The APTS/PA6 solution coated magnetic nanoparticles showed better electrospinning performance than the other structures. The dispersion and the morphology of the magnetic nanoparticles in the PA6 nanofiber matrix were investigated using SEM, energy-dispersive X-ray, and transmission electron microscopy. In addition, the thermal stability and magnetic behavior of these nanoparticles were assessed using thermal gravimetric analysis and vibrating sample magnetometer, respectively. The introduced preparation method in this work not only provides nanofibers with controlled size but also homogeneously dispersed the magnetic nanoparticles within the fibers. The combination of high magnetic properties with outstanding thermal stability as presented by the obtained magnetic nanofibers in this study is very promising in the diagnosis and therapy of cancer. POLYM. COMPOS., 00:000–000, 2017. © 2017 Society of Plastics Engineers

Modification of carbon fibers surfaces with polyetheramines: The role of interphase microstructure on adhesion properties of CF/epoxy composites


Interface construct plays a vital role in developing superior mechanical performance of carbon fibers (CFs)/resin composites. Herein, a facile approach for incorporation of polyetheramine (PEA) onto CFs surface by covalent bond (CF-g-PEA) was proposed, and compared to the adsorption one via Van der Waals' force (CF-c-PEA). FTIR, X-ray photoelectron spectroscopy, Raman spectra, scanning electron microscopy, atomic force microscopy, dynamic contact angle analysis, single fiber tensile testing, and interfacial shear strength were carried out to characterize the CF reinforcements and composites. Experimental results showed that both of coating and grafting PEA on CFs increased the polarity, wettability, roughness of CF surface, and interfacial shear strength, especially CF-g-PEA, which indicated covalent bond interaction can combine more PEA on CF surface than that of Van der Waals. While single fiber tensile strength of CF-c-PEA increased due to the structure of CF without destruction. Meanwhile, the reinforcing mechanisms and interfacial failure modes of composites were also explored. The results suggest that the interphases between the CFs and resin matrix can be adjusted by varying the bonding natures between CF and grafted modifiers, thereby offering a new route for appropriate designing and development of CF-based composite materials. POLYM. COMPOS., 00:000–000, 2017. © 2017 Society of Plastics Engineers

Exploring the effect of electron beam irradiation on the properties of some EPDM-flax fiber composites


Composites based on ethylene propylene diene rubber (EPDM) loaded with different contents of flax fibers were irradiated using accelerated electron beams at various irradiation doses (75, 150, 300, and 600 kGy). The mechanical, physical, thermal properties, and morphology were analyzed as a function of e-beam irradiation dose and natural fiber loading. Also, crosslink density, gel fraction, and water uptake were investigated to characterize the EPDM/fiber composites subjected to e-beam irradiation. It was noted that the irradiation dose had a positive influence on hardness, 100% modulus and tensile strength, but an inverse effect was found on the elongation at break and elasticity. The crosslink density was estimated based on equilibrium solvent-swelling measurements using the Flory-Rehner relation. The kinetic parameters of thermal decomposition were determined applying the Flynn-Wall-Ozawa isoconversional method. POLYM. COMPOS., 00:000–000, 2017. © 2017 Society of Plastics Engineers

Effect of fiber orientations of composite panels under far-field pyroshock


The effect of different fiber orientations of composite panels of E-Glass/Epoxy under far-field pyroshock is presented in this article. To get the far-field pyroshock response, the experiments are conducted using Bi-plate technology under low range of input chamber pressures to projectiles of three different lengths. PCB accelerometers and NI-DAQ system with LabView software are used to capture the structural responses in the form of acceleration-time histories and analyze them at selected locations. Abaqus/Explicit code is used in the Finite Element Analysis (FEA) for the pyroshock response of composite panels with different fiber orientations. From the results, it is found that the selected locations on the [0/90/±45]s WRM (Woven Roving Mat) laminate experience higher accelerations, above 30% extra, than other fiber orientations. Since [0/90/±45]s laminate has lengthier fiber rovings along the diagonal direction, higher Young's modulus along the fiber direction and the most vibration modes are diagonally biased, the response amplitude would be high enough to experience maximum acceleration. The acceleration responses are obtained both from FEA and experiments and show good agreement. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Effect of graphene nanoplatelets structure on the properties of acrylonitrile–butadiene–styrene composites


In this study, the effects of various types of commercial graphene nanoplatelets (XG Sciences xGnP M5, C300, C500, and C750) on the thermal, electromagnetic shielding (EMI SE), electrical and mechanical behavior of an acrylonitrile–butadiene–styrene (ABS) copolymer matrix were investigated. The selected nanofillers were characterized and compared in term of surface area, different oxygen content, dimension and density (X-ray photoelectron spectroscopy, scanning electron microscopy, and helium pycnometry). Graphene nanoplatelets were dispersed in ABS by direct melt compounding at 2, 4, and 8 wt%. Melt flow index (MFI) values almost linearly decreased with all the type of xGnPs, especially with the highest surface area nanofiller (C750). Moreover, EMI SE of neat ABS was improved from −0.7 dB to −2.5 dB (increase more than 3 times) for xGnP (C300, C500, and C750) and to −6.2 dB (increase about 9 times) for xGnP-M5, in agreement with proportional reduction of electrical resistivity. xGnP-M5 also resulted in being most effective in enhancing the tensile modulus which improved up to 64%, while a maximum increment of about 20% was obtained with the others xGnP nanoparticles. However, yield stress slightly decreased for xGnP-M5 (about −9%) and remained fairly constant for others nanofillers. Halpin–Tsai model used to predict the tensile modulus of the nanocomposites suggested that graphene nanoplatelets were randomly oriented in the ABS matrix in a three-dimensional (3D) manner. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Prediction of filler/matrix interphase effects on AC and DC electrical properties of carbon reinforced polymer composites


This study predicts the effect of the conducting filler/insulating matrix interphase on the electrical properties of two series of percolated systems, differing from the type of carbon black particles mixed in an amine-cured epoxy matrix, diglycidylic ether of bisphenol F. To take into account the interactions between the conducting filler and the matrix, as well as filler–filler overlapping, we introduce three parameters, characteristic of the interphase zone, such as concentration, conductivity and volume, on the generalized effective medium (GEM) model for DC and AC electrical conductivities. These interphase parameters, characterizing the boundary of the shaded zone between the macromolecular chain and the conducting particles, depend on the filler type and concentration. One output of GEM-modified model is that it provides a mean to estimate the volume, concentration and intrinsic conductivity of the interphase in a composite by fitting the experimental data over a broad range of frequency. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Assessment of modified rice husk powder/ethylene propylene diene monomer (EPDM) nanocomposites for biomedical applications


The nanocomposite of nano rice husk powder (nRHP)–ethylene propylene diene monomer (EPDM) was prepared from modified nRHP and EPDM with different formulations containing 0–100 parts of modified nRHP per 100 parts of EPDM using curing process and laboratory size two roll mill. The surface of nRHP was modified by grafting MA-g-EPDM copolymer on its surface to enhance the compatibility between nRHP and EPDM. MA-g-EPDM copolymer was successfully prepared by melt method. The effect of filler (nRHP) loading on the mechanical and morphological properties of the modified nRHP–EPDM nanocomposites was investigated compared to the unmodified nRHP–EPDM nanocomposites (blank). Successive study was carried out on the nRHP–EPDM nanocomposites by means of human gingival fibroblast (HGF) as a fine source of human cell lines to test the cytotoxicity of the prepared nanocomposites by using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT). The in vitro study indicated that the prepared nanocomposites were non-toxic for HGF and could be developed for future medical uses. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Covalent functionalization of MWCNT with PHBV chains: Evaluation of the functionalization and production of nanocomposites


Multi-walled carbon nanotubes (MWCNT) were covalently functionalized with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) chains, through esterification reaction. Thereunto, pristine MWCNT (P-MWCNT) were oxidized (MWCNT-COOH) and posteriorly reduced (MWCNT-OH). MWCNT-OH were used to produce MWCNT functionalized with PHBV chains (MWCNT-PHBV). All functionalized MWCNT were used to produce PHBV nanocomposites films with 0.5 wt% by solution casting. Functionalization was evaluated by Raman spectroscopy and thermogravimetry (TGA), and nanocomposites were characterized by X-Ray Diffraction and contact angle measurements. Results showed that functionalization with PHBV chains was successfully performed and that the polymer chains were attached to MWCNT surface, as expected. IG/ID ratio obtained from Raman curves was reduced from 1.34 to P-MWCNT to 0.90 to MWCNT-PHBV. TGA confirmed the presence of PHBV on MWCNT surface, showing a peak at 236°C on the first derivative curve. Crystallite size of PHBV on 020 plane was 11% larger with introduction of MWCNT in nanocomposites. Contact angle was increased with the introduction and functionalization of MWCNT. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Preparation of hybrid composites based on epoxy, novolac, and epoxidized novolac resins and silica nanoparticles with high char residue by sol-gel method


A facile method was developed for preparation of three hybrid composites by using tetraethyl orthosilicate oligomer-modified epoxy resin (MER), (3-glycidyloxypropyl) trimethoxysilane-modified novolac resin (MNR), epoxidized novolac resin (ENR), and silica nanoparticles (SiO2). Accordingly, the first class of composites was prepared from MER and SiO2. The second class of composites was prepared from MER, MNR, and SiO2. And the third class of composites was prepared from silica MNR, ENR, and nanoparticles. All the modified resins and their composites were characterized by Fourier-transform infrared spectroscopy and their thermal behavior was investigated by thermo gravimetric analysis. The obtained thermograms showed that thermal stability of hybrid composites were controlled by the amount of SiO2 and type of resins. Char yield of epoxy resin was increased significantly by formation of hybrid composites. The second class of composites showed higher char yields in comparison with the first class (52.1 compared with 23.2% for 8 wt% of SiO2). Incorporation of ENR instead of MER in the third class composites resulted in much more char residues of 60.2 and 60.6% for 4 and 8 wt% of SiO2. Therefore, third class composite with 8 wt% of SiO2 exhibited the highest char yield. Scanning electron and transmission electron microscopies were used to study the morphology and dimension of SiO2. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Flexural and fracture behavior of natural fiber knitted fabric reinforced composites


Decreasing natural resources and increasing environmental destructions dispatch researchers to find more ecological solutions in material industry. Natural fibers have recently become an interesting topic as an alternative reinforcement material for fiber reinforced polymer composites for researchers. In this study; the effect of knitting density, natural fiber type, crack length, and fabric direction (wale or course) on the fracture strength and fracture toughness of laminated composites reinforced with natural fiber knitted fabric were investigated. For this aim, plain fabrics made of 50/50 bamboo/cotton, 50/50 viscose/cotton, and 50/50 modal/cotton blended yarns were knitted with three different knitting density. After that; bamboo/epoxy, viscose/epoxy, and modal/epoxy laminated composites were produced by using hand lay-up method. Quasi-static three-point bending tests have been carried out on the single-edge notched bending composite specimens, which have a crack in wale or course directions. Fractured surfaces investigated through the Scanning Electron Microscopy describing different failure mechanisms are also reported. Test results showed that fabric which knitted in cellulosic fibers, reinforced composites, had higher flexural strength and fracture toughness in the wale direction. It has also been observed that the knitting density and crack geometry affect the crack propagation behavior. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Reinforcing effects of functionalized graphene oxide on glass fiber/epoxy composites


Glass fiber (GF)/epoxy (EP) matrix composites containing graphene oxide (GO) nanoplatelets were manufactured for improving the mechanical properties. GO nanoplatelets were functionalized using dodecylamin (DA) and 1-(3-aminopropyl) imidazole (IL) to improve their dispersion in the matrix and to reinforce EP adhesive. The structural properties of GO and functionalized GOs (FGOs) were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction and BET surface area measurements. In the sample preparation, 3-ply composites were prepared by hand lay-up process, using a fiber-to-resin ratio of 40:60 (w:w). The high performance GO and FGOs were next incorporated into EP matrix resin to generate the reinforced GO/EP/GF and FGO/EP/GF composites. The GO and FGO contents varied in the range of 0.3, 0.5, and 0.8 wt%. Decreasing of oxygenated functional groups on FGOs and the appearance of aminated groups were proved by the FT-IR spectra. The specific surface area of DA-GO (295.8 m2/g) was much larger than IL-GO (42.88 m2/g) or GO (2.49 m2/g), indicating a better interfacial interlocking of the DA-GO in EP matrix. In addition, the BET surface areas of the FGOs were increased as compared to that of GO, which could be ascribed to the addition of functional groups on the GO sheet. Results showed that the mechanical properties, in terms of tensile and flexural properties, were mainly dependent on the type of GO functionalization followed by the percentage of modified GO. As a result, both the tensile and flexural strengths are effectively enhanced by the FGOs addition. However, the reinforcing effect of DA-GO on the mechanical properties was much better than IL-GO and GO nanoparticles. The tensile and flexural moduli are also increased by the FGO filling in the EP resin due to the excellent elastic modulus of FGO. Although incorporating FGO into the EP matrix effectively improves mechanical properties, this improvement comes at proper loading. The optimal DA-GO and IL-GO contents for effectively improving the mechanical performance were found to be 0.5 and 0.8 wt%, respectively. Scanning electron microscopy confirmed that the failure mechanism of GFs pulled out from the EP matrix contributed to the enhancement of the mechanical performance. These results show that FGOs can strengthen the interfacial bonding between the GFs and the EP adhesive. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Preparation of poly(vinyl alcohol)/poly(lactic acid)/hydroxyapatite bioactive nanocomposites for fused deposition modeling


Poly(vinyl alcohol)/hydroxyapatite (PVA/HA) has excellent mechanical properties and osteoconductivity that allow it to be used for cartilage repair. However, nanofillers, such as HA, cause PVA to foam during the extrusion process, making it difficult to produce filament feedstocks with uniform diameters that are suitable for fused deposition modeling (FDM). In this article, a novel method was developed to prevent the foaming of PVA-based nanocomposites during extrusion by selectively distributing HA in the poly(lactic acid) (PLA) phase. To achieve this, HA was treated with 3-Glycidoxypropyltrimethoxysilane (KH560). The results showed that HA treated with KH560 was segregated from the PVA phase, thus preventing the foaming of PVA. Finally, filament feedstocks with a uniform diameter of 1.75 ± 0.05 mm, which is suitable for FDM, were successfully fabricated. Meanwhile, a mathematical equation for characterizing the printability of feedstock materials was improved. The results indicated that in combination with PLA, composites with a higher compressive modulus and better melt flowability were able to be processed by FDM. Finally, complex PVA-based bioactive nanocomposite scaffolds with high dimensional accuracy, good mechanical properties, and biocompatibility were fabricated by the FDM machine. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Depth-sensing indentation and nano-dynamic mechanical properties of aluminum nitride nanoparticles reinforced high density poly-ethylene nanocomposites


Inorganic aluminum nitride (AlN) nanoparticles offer numerous innovative applications in the field of electronic packaging due to its outstanding features; viz., high mechanical strength, stable crystal structure, excellent thermal conductivity, low coefficient of thermal expansion, low-cost, and non-toxicity. In this research, attempts have been made to investigate the effect of reinforcement of nano-AlN particles in high density poly-ethylene (HDPE) thermoplastic polymer on their nano-mechanical properties using depth-sensing indentation (DSI) technique. Polymer-matrix nanocomposites composed of pure HDPE and 1–20 vol% nano-AlN/HDPE composites are prepared via melt mixing followed by compression molding. Surface-morphology and crystallinity of HDPE/nano-AlN composites are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). Nano-scale hardness, modulus of elasticity, storage modulus, and loss tangent (tanδ) of HDPE/nano-AlN composites have been evaluated using static and dynamic-DSI. Both static and dynamic-DSI results indicate that with increasing concentration of AlN nanoparticles in pristine HDPE, the nano-mechanical properties display significant improvement. Results are discussed in relation to the surface-morphology, crystallinity and interfacial adhesion between pure HDPE and nano-AlN particles. A comparison between nano-mechanical data extracted from static-DSI and dynamic-DSI techniques analysis is also attempted. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Preparation and characterization of poly(amide-imide)/Mg-Al LDH nanocomposites; effect of organo-modified LDH on thermal properties and morphology


New poly(amide-imide) Mg-Al/layered double hydroxide (LDH) nanocomposites (PAINC) were prepared from synthesized poly(amide-imide) (PAI) containing sulfone and ether linkages with two new organo modified Mg-Al LDH (OLDH) by solution intercalation technique. OLDH were prepared from two different organo modifier with and without imide heterocyclic structure by one step method. The results of X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) showed uniform distribution for LDH sheets in the PAI matrix. Thermal properties of all the samples were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal properties results showed that by OLDH loading in PAI matrix the thermal stabilities were increased. The temperature at 5% mass loss (T5) was increased from 225°C to 300°C for PAINC containing 5 mass% of OLDH containing imide hetrocyclic rings. The theoretical study indicated that the d-value of OLDH has been related to structure of its organo-modifier. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Nanoclay decorated polyacrylic acid/starch hybrid nanocomposite thin films as packaging materials


Nanoclay reinforced starch-co-PAA hybrid nanocomposite thin films are synthesized by in situ polymerization technique in aqueous solution. The interactions of clay with starch-co-PAA are studied by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The morphology of nanoclay platelets in starch-co-PAA hybrid nanocomposite thin film is studied by scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) images are used to investigate micro and nanostructural behavior of clay platelets in starch-co-PAA matrix. It is noticed that, the thin film has an exfoliated structure at 3 wt% clay loading whereas; clay platelets are agglomerated in higher percentage of clay. The synthesized materials have chemical resistance of 22% more than the virgin matrix. The biodegradable properties of the nanocomposite thin films are reduced by 20% due to incorporation of nanoclay. The oxygen barrier property of starch-co-PAA/clay thin film is reduced by seven folds as compared to starch-co-PAA. From the measurement of refractive indexes, it is found that, the transparency of the nanocomposite thin films are reduced by around 10% by reinforcement of nanoclay. The results show a substantial enhancement in oxygen barrier property and reduction of refractive index on clay loading, which may permit the synthesized materials suitable for packaging applications. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Effect on thermo-mechanical properties by in-situ emulsion polymerization of polymer/clay nanocomposites


Bentonite clay nanoparticles without surface modification were used to prepare a polymer-based nanocomposite: Butyl acrylate (BA), methyl methacrylate (MMA), and acrylic acid (AA) were copolymerized as the matrix. The synthesis was carried out using seeded batch emulsion polymerization system. Bentonite was added up to 3 wt% and the metastable emulsions remained for a period over 6 months in storage at room temperature, to estimate the emulsion stability. Cast films were obtained from the aqueous dispersions and these were optically transparent. Scanning electron microscopy and X-ray scattering spectra showed that the copolymer chain had intercalated the Bentonite nanoplatelets, with aggregates into small crystalline clusters and dispersed through the polymer matrix. Differential scanning calorimetry showed that increasing the concentration of Bentonite increased the glass transition temperature, Tg. Furthermore, uniaxial tensile deformation at room temperature showed that the elastic Young's modulus, E, increased over an order of magnitude at 3 wt% Bentonite concentration. These results suggest that the molecular dynamics is inhibited, due to the associated restricted motions of the confined macromolecules within the gallery clay and the increment of the molecular weight. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Modification of TiO2 with graphene oxide and reduced graphene oxide; enhancing photocatalytic activity of TiO2 for removal of remazol Black B


Modified titanium dioxide (TiO2) nanoparticles with graphene oxide (GO) and reduced graphene oxide (rGO) were prepared using the chemisorption process. The characterization was carried out by IR, X-ray diffraction spectra, scanning electron microscopy, energy dispersive X-ray spectroscopy, and DRS techniques. The photocatalytic activity of GO/TiO2 and rGO/TiO2 nanocomposites was evaluated in photodegradation of Remazol Black B (RBB). The effects of various parameters, such as pH, adsorbent dosage, dye concentration, and contact time, were studied in a batch system. The results showed that GO/TiO2 and rGO/TiO2 nanocomposites can extend the absorption of light to the visible region and makes the photocatalysts active under visible-light irradiation. Photocatalytic activity clearly showed that the modification of TiO2 nanoparticles by GO and rGO enhanced the degradation of RBB from the aqueous solution (99.9% dye removal). Photodegradation processes fitted well with the pseudo-first-order kinetic model (R2 > 0.99). POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Influence of in situ synthesized bismuth oxide nanostructures in self-poled PVDF-based nanogenerator for mechanical energy harvesting application


A self-poled piezoelectric nanogenerator (NG) based on bismuth oxide (Bi2O3) nanostructures (BNS)-doped poly(vinylidene fluoride) (PVDF) is demonstrated. The in-situ formation of BNS incorporated in the PVDF matrix is realized through a simple solution casting technique that favors the nucleation and stabilization of 99.6% of the electroactive phase in PVDF (i.e., β/γ-phases). The enhancement of the output voltage (3.6 V) and current (2.4 µA) of the NG based on a nonelectrically poled BNS containing PVDF composite film is achieved and demonstrated by simple repeated human finger imparting. The improvement of the output performance is influenced by the generation of the electroactive polar β-phase in PVDF, due to the electrostatic interactions between the –CH2–/–CF2– dipoles of PVDF and the surface charge of the BNS. The NGs are able to charge up capacitors demonstrating that the power generation from such a hybrid device structure can be utilized for powering various portable devices. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Hybrid biocomposites


Composites are primarily made using matrix and reinforcement as major components but may also contain several other fillers or additives. A majority of the composites are made using synthetic fibers and polymers. However, in the last few decades, focus has been on developing biocomposites using renewable resources. Conventionally, biocomposites are developed using natural fibers such as jute, Kenaf, or Ramie as reinforcement and synthetic resins such as polyethylene, polypropylene and epoxy as matrix. Typically, biocomposites contain either the reinforcement or matrix which makes the composites partially degradable. Such partially degradable composites provide good properties, but the presence of a nonbiodegradable component, particularly as a matrix limits their biodegradability. Alternatively, composites that contain both the matrix and reinforcement from renewable resources which make the composites completely degradable have also been developed. However, these completely biodegradablebiocomposites do not have the desired mechanical properties and stability at high humidities or in aqueous environments which restricts their application. In addition, natural fibers and resins used in biocomposites have inherent limitations and also not easily processable. To overcome limitation of using a single reinforcement or matrix derived from bioresources, hybrid composites that contain more than one reinforcement or matrix are developed. Such hybrid composites are manufactured by either intimately mixing two or more fibers or other reinforcing materials or by placing different layers of the reinforcement and molding them into composites using one or more resins. Conventionally, hybrid composites refer to metallic and ceramic based reinforcement, matrix and fillers. Although hybrid biocomposites are gaining significant attention, the presence of multiple reinforcements and/or matrix makes it difficult to process and also to predict the properties of such composites. Hence, understanding the properties and potential of using multiple reinforcements and/or matrix materials from renewable resources to develop biobased hybrid composites is highly desirable. This article discusses hybrid composites that contain a major proportion of renewable materials. Hybrid composites not only provide better properties but could also lead to substantial cost reduction due to the incorporation of inexpensive raw materials. These composites show potential for use in aeronautical, sporting goods, wind power turbine blades, helmets and civil construction such as pedestrian bridges and many other applications. This review provides an overview of the biobased materials used to develop hybrid composites, their processability and their potential applications. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

PHBV/CNC bionanocomposites processed by extrusion: Structural characterization and properties


Bionanocomposites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with cellulose nanocrystals (CNC) were processed by extrusion. Differential scanning calorimetry (DSC) showed that with increasing the amount of CNC the overall crystallization time was reduced. Wide angle X – ray scattering (WAXS) showed diffraction peaks of orthorhombic α– type crystalline structure and confirmed the nucleating agent effect of CNC particles in the PHBV matrix. Small angle X-ray scattering (SAXS) showed that the reducing rate of long spacing was slower in the filled sample than in PHBV. Microscopy images (Scanning Electron Microscopy, SEM, and Transmission Electron Microscopy, TEM) revealed well-dispersed morphology in low loading of the filler while slight agglomerations appeared at higher filler concentration. Statistical analysis was done by applying a one-way ANOVA (α = 0.05) to evaluate the effect of filler on mechanical properties of PHBV. Water vapor, oxygen and carbon dioxide transmission rate showed that the incorporation of CNC nanocrystals led to an improvement in the barrier properties of the bionanocomposites due to higher crystallinity and more tortuosity in their morphologies. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Electrified single-walled carbon nanotube/epoxy nanocomposite via vacuum shock technique: Effect of alignment on electrical conductivity and electromagnetic interference shielding


Electrified and non-electrified epoxy-based nanocomposites holding highly and randomly aligned single-walled carbon nanotube (SWCNT), respectively, were made by vacuum shock technique, where a DC electric field was used to align SWCNT. The alignment of SWCNTs in the electrified nanocomposites was verified via optical microscopy, SEM analysis, and Raman spectroscopy. Electrical characterization revealed that alignment of SWCNTs led to a significant improvement in electrical conductivity and electromagnetic interference shielding of the fabricated nanocomposites. For instance, the electrical conductivity of the electrified nanocomposites at 0.25 wt% and 0.60 wt% was 2.5 × 10−8 and 5.1 × 10−4 S·m−1, while the conductivity of non-electrified nanocomposites was 1.1 × 10−11 and 5.6 × 10−5 S·m−1, respectively. With 3.0 mm thickness and 0.60 wt% SWCNT loading, the electrified and non-electrified nanocomposites showed shielding effectiveness of 12.8 dB and 9.1 dB, respectively. These results revealed that electrification of SWCNT in epoxy-based nanocomposites improved the level of conductive network formation, thereby enhancing electrical properties of the nanocomposites. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

In situ reduction of graphene oxide in the poly (vinyl alcohol) matrix via microwave irradiation


Despite great recent progress, the processing of graphene oxide (GO) sheets in polymers are often one of the most challenging steps in fabricating graphene/polymer nanocomposites. The challenge is how to achieve high levels of dispersion and reduction of GO simultaneously, without any residual reducing agents in the composites. In this work, microwave irradiation is applied as a remote source to in situ reduce GO sheets embedded in the poly (vinyl alcohol) (PVA) matrix, which process maximizes the advantage of GO's solvent processability. The active response of GO to microwave irradiation allows for the uniform and selective heating of GO, leading to a minutes-quick reduction of GO without physical damage to the polymer matrix. Significant improvements in the mechanical properties, electrical conductivities and glass transition temperatures (Tgs) of GO/PVA nanocomposites are achieved, and possible reasons for the improvements are also discussed. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Study on mechanical properties of unidirectional continuous carbon fiber-reinforced PEEK composites fabricated by the wrapped yarn method


The purpose of this study was to investigate the mechanical properties of unidirectional continuous carbon fiber-reinforced PEEK (CCF/PEEK) composites via the wrapped yarn method and to obtain optimum fabrication conditions. The composite plates were fabricated at different processing conditions and their mechanical properties (i.e., tensile, bending and short beam shear strength performance) were investigated in terms of thermal and fracture morphology characterizations. As the molding temperature and molding time increased, the mechanical properties of the composites enhanced due to the improved impregnation of the fibers, although there was potential matrix degradation. Moreover, slow cooling rate had little effect on the mechanical properties of the composites. Therefore, to obtain a combination of excellent mechanical properties and high production efficiency, a relatively high molding temperature, sufficient molding time and moderate cooling rate were optimal for the CCF/PEEK fabricated by the wrapped yarn method. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Synergistic effect of halloysite nanotubes on flame resistance of intumescent flame retardant poly(butylene succinate) composites


A novel intumescent flame retardant poly(butylene succinate) (IFR-PBS) with antidripping property was prepared using halloysite nanotubes (HNTs) as the synergistic agent. Ammonium polyphosphate (APP), melamine (MA), pentaerythritol (PER), and halloysite nanotubes (HNTs) were added in PBS via melt blending. The effects of HNTs as the synergistic agent on the flame retardancy property, thermal property, and mechanical property of IFR-PBS composites were investigated. Cone calorimetry revealed that partial substitution of IFR by HNTs (1.5 wt%) substantially improved the flame retardancy of IFR-PBS with a reduction of heat release rate (HRR), total heat release (THR), and total smoke production (TSP). In addition, the limiting oxygen index value was increased from 42.1 to 58.2 with only 1.5 wt% addition of HNTs. The incorporation of HNTs also enhanced the thermal stability of the IFR-PBS composites and reinforced the composites. Scanning electron microscopy (SEM) results showed that the composite containing HNTs had a tighter protective char layer after cone calorimeter test, which protected the underlying polymer from the external heating. Overall, the results indicated that suitable amounts of HNTs had a noticeable synergistic effect on the flame retardancy property of IFR-PBS composites. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Theoretical prediction for thermal expansion coefficients of unidirectional fiber-reinforced composites with variable elliptical cross-sections


A three-dimensional theoretical model is established to predict the coefficients of thermal expansion for unidirectional fiber-reinforced composites. Based on ellipse cross-sections to approach to the actual state of transversely isotropic fibers, this thermo-elastic mechanics analysis reveals the influence of fiber azimuth angular variation, which is superior to other known theoretical solutions. Taking different material systems and some other theoretical solutions into consideration, we could find the theoretical predictions are consistent with the results of the finite element method and existing experiments and the proposed model offers better agreements. Particularly, we focus on the overflow phenomenon of the transverse coefficient at low fiber volume fractions, contributing to developing fiber-reinforced composite designability. For adapting to irregular fiber shape, this article is innovative with the fiber shape factor concept as the main point of cross-section shape effect. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Preparation and properties of MNSiO2/CN40/PF nanocomposites


MNSiO2/CN40/PF nanocomposites have been fabricated in this study. Nano-SiO2 was initially surface-modified with γ-methacryloxypropyl trimethoxysilane (MPS). The resulting nano-SiO2 was denoted as MNSiO2. Core-shell composites, MNSiO2/CN40, was fabricated by a solution blending method, in which MNSiO2 served as the core and liquid acrylonitrile butadiene rubber (CN40) served as shell. Phenol formaldehyde resins (PF) were prepared by means of condensation polymerization method. MNSiO2/CN40/PF hybrid with a fixed weight ratio (2:98) of MNSiO2/CN40 composites to PF were prepared by a modified routine of preparation of pure PF. MNSiO2/CN40/PF nanocomposites were prepared by incorporating filler particles with MNSiO2/CN40/PF hybrid via melt blending, followed by compression molding method. The impact of MNSiO2 content on the properties of the MNSiO2/CN40/PF nanocomposites was systematically investigated by varying the weight ratio of MNSiO2 to CN40 in MNSiO2/CN40 core-shell composites. The results revealed that MNSiO2/CN40 significantly enhanced the mechanical and frictional properties of the as-prepared MNSiO2/CN40/PF nanocomposites. Compared to pure PF, the impact strength of MNSiO2/CN40/PF hybrid containing 1.0 wt% of MNSiO2 in MNSiO2/CN40 composites increased by 29.2%, and the initial storage modulus was enhanced dramatically. In addition, MNSiO2/CN40/PF hybrid demonstrated stable friction coefficient, while the wear mechanism of pure PF was adhesive and fatigue wear. The MNSiO2/CN40/PF nanocomposites exhibited a combination of adhesive, abrasive, and fatigue wear. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Directional diffusion of moisture into unidirectional carbon fiber/epoxy Composites: Experiments and modeling


Water diffusion into composites in different directions was examined in this study with the aim of determining the best way of measuring diffusion coefficients and to provide values to compare with model predictions. Water absorption behavior of unreinforced epoxy resins and carbon fiber reinforced epoxy composite materials was investigated with long-term exposure to different environmental conditions. Initial Fickian absorption was observed followed by a slower second stage that continues for at least 3.7 years. Fiber architecture was found to be an important aspect of controlling absorption, where water diffusion along fibers was observed to be about three times faster than across the fibers and about seven times faster than through the thickness. A three-dimensional finite element computer model based on Fickian diffusion behavior was developed to predict the levels of moisture absorption under hot/humid environments. A multi-scale modeling approach was used which allowed the results of simulations at the micro-structural level to be used to predict the diffusivity in different directions. The modeled diffusion coefficients showed high dependency on the detailed micro-structure. Experimental results provided a baseline for the validation of the model, and it was found that these data could be closely predicted using a reasonable micro-structure characterization. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Mixed mode morphology in elastomeric blend nanocomposites: Effect on vulcanization, thermal stability and solvent permeability


The localization of organically modified nanoclays in chlorobutyl rubber (CIIR) and natural rubber (NR) blend system was carefully studied by following the vulcanization behaviour, morphology, thermal and solvent permeation characteristics. From the vulcanization studies, it was observed that incorporation of nanoclay platelets significantly affected the viscosity and vulcanization parameters such as cure time, scorch time, rate of cure and the degree of cure. Thermal analysis pointed out that the addition of nanoclay increased the thermal stability of the elastomer blends. The morphology of the blends indicated that the nanoclay platelets were localized at the interface and in both phases (mixed mode morphology) of elastomer blends and this affected the overall properties. The transport characteristics of NR/CIIR blend nanocomposites using toluene as the solvent were also studied. The transport parameters such as the equilibrium uptake, diffusion coefficient and the rate constant have been computed. The transport characteristics have been correlated with the microstructure of the blend nanocomposites. Finally, applied the Peppas–Sahlin model to fit the experimental diffusion data and the fitting was found to be reasonably good. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Effect of morphology development on the crystallization behavior, dynamic mechanical properties, and toughness of the PA-6/plasticized PVB/organoclay nanocomposites


PA-6/PVB blends and related nanocomposites with organoclay were prepared via melt-processing and structure-property relationships were comprehensively investigated. The SEM observations showed that blend composition and organoclay content play significant roles in the development of morphology. The differential scanning calorimetry results revealed occurrence of fractionated crystallization in the blends due to development of co-continuous morphology. In contrast, the degree of fractionated crystallization decreased in the nanocomposites owing to role of the nanoclay as heterogeneous nucleating agent. It was found that there is an interesting relationship between morphology development and dynamic mechanical properties of the blends. Furthermore, the effects of the morphology development and nanoclay on the viscoelastic behavior of the nanocomposites were synergistic and/or counteracting depending on the Cloisite 30B content. The PA-6/PVB blends with co-continuous morphology showed outstanding toughness. In addition, the PA-6/PVB50 blend with low nanoclay concentration exhibited high impact strength, which was originated from low interparticle distance between PVB domains in the matrix. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Biodegradability, flammability, dimensional stability, and UV resistance study of green wood starch gluten nanocomposites


Biodegradable and UV resistant wood starch gluten nanocomposites (WSGNC) were prepared successfully from the natural polymers like starch and gluten, natural crosslinker and natural solvent via a green route using solution blending technique followed by compression molding. In this procedure, the starch gluten (50/50) blend was grafted with methyl methacrylate (MMA-g-SG) and citric acid was used to crosslink the MMA-g-SG with wood flour from Ipomoea carnea using water as a solvent. Later, Nano TiO2 was added in the composites to improve the properties like UV stability and flammability. The effects of TiO2 nanoparticles on biodegradability and UV stability of the composites were thoroughly investigated. The bacterial growth on the samples was analyzed by UV spectrophotometry and morphological features of the bacterial degraded samples was investigated by SEM study. The UV-degraded samples were analyzed by FTIR and SEM study. It was observed that the incorporation of 3 phr TiO2 in the composites significantly improved the UV stability and hardness values of the composites. The flammability and dimensional stability of the nanocomposite were also improved with 3 phr nano TiO2 loading compared to TiO2-untreated composites. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Radiation attenuation capability and flow characteristics of HDPE composite loaded with W, MoS2, and B4C


Shielding radiation from both x-rays and gamma-rays is important for personnel in medical fields, for example, interventional radiology, nuclear power stations, and other facilities where radiation is involved. Lead is known for its effective shielding property; however heaviness and toxicity are its main drawback. In this study effectiveness of non-lead polymeric composite materials, which include high-atomic-number (powders of spherical W and lamellar MoS2)/or known barrier elements to absorb photons from the radiations (lamellar B4C) was evaluated. HDPE and particulate fillers were melt mixed in an internal mixer. Goodness of dispersion was manifested via SEM and EDX images. Radiation attenuation capability of samples was examined with direct diagnostic x-ray exposure. Dynamic rheology measurements were carried out to evaluate viscoelastic properties, necessary in shaping process operations. Mechanical and thermal properties were further investigated from the product performance point of view. Results demonstrated that the flexible composite sheet of HDPE/45% (wt) W provided comparable x-ray absorption to non-flexible lead sheet but much lighter in weight. Significant difference was observed between flow characteristics and yield strength of composite materials of highly loaded spherical and lamellar particles. Melt viscoelastic behavior of former was similar to that of neat matrix melt. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Fabrication of flame retardant benzoxazine semi-biocomposites reinforced by ramie fabrics with bio-based flame retardant coating


Natural fibers reinforced benzoxazine bio-composites are one class of highly attractive engineering materials in automobile, train and aerospace fields because of high thermal stability, good mechanical and improved biodegradability properties. Unfortunately, their poor interface and flammability issues remain unsatisfactorily addressed to date. Herein, we have demonstrated the fabrication of benzoxazine semi-biocomposites reinforced by ramie fabric which was coated with bio-based poly(diphenolic acid-phenyl phosphate) (poly[DPA-PDCP]) and polyethylenimine (PEI) via layer-by-layer self-assembly method. The results show that the presence of poly(DPA-PDCP)/PEI coating can significantly improve the interfacial adhesion between fabric and the resin matrix. This enables the tensile strength and flexural strength of as-prepared semi-biocomposite to increase by 53% (68.7 MPa) and 113% (120 MPa), respectively. In addition, the resultant semi-biocomposite shows superior flame retardancy with a V-0 rating achieved in the UL-94 test. This work offers an effective approach to fabricate strong and flame retardant benzoxazine semi-biocomposites. POLYM COMPOS., 2017. © 2017 Society of Plastics Engineers

Magnet assisted composite manufacturing: A novel fabrication technique for high-quality composite laminates


A novel fabrication method, Magnet Assisted Composite Manufacturing (MACM), is developed to produce high-quality composite laminates out of an autoclave. This technique involves the placement of high-temperature Neodymium permanent magnets on a vacuum bag to generate sufficiently high consolidation pressure during cure, thus eliminating the necessity of using an autoclave. The objective of this study is to demonstrate the ability of MACM to fabricate high-performance laminates, which have comparable mechanical properties, fiber volume fraction, and void content to those achieved by autoclave curing. Towards this goal, eight-ply, woven carbon/epoxy laminates were fabricated in an oven by MACM and in an autoclave using the same thermal cycle. The thickness of the laminates cured by MACM indicated that an effective consolidation pressure of 0.29 MPa (42 psi) can be generated by the magnets during cure at 177°C (350°F). The high flexural properties, high fiber volume fraction, and the low void content of the laminates fabricated by MACM validated the feasibility of this process as a lower-cost alternative to autoclave cure, without compromising the part quality. Considerable reduction of void content to under 1% was also achieved by applying magnets during cure when the resin viscosity was at a minimum. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

High-concentration polybenzimidazole-assisted exfoliation of boron nitride nanoflakes for polymer composites


In this article, we present a facile method for fabricating high thermally conductive and high-strength polybenzimidazole/boron nitride nanoflakes (BNNS) composites. In brief, based on the method of liquid-phase exfoliation, the polybenzimidazole functionalized BNNS (f-BNNS) were facile obtained by directly sonicating the bulk hexagonal boron nitride (h-BN) flakes/dimethylsulfoxide dispersion in presence of polybenzimidazole. The yield concentration of exfoliated BNNS can facile reach a high concentration of ∼1.43 mg/mL after direct sonication of 10 h with assistance of polybenzimidazole. By means of solution casting, the obtained f-BNNS/polybenzimidazole composite films shows higher thermally conductivity and mechanical property compared to that of hexagonal boron nitride/polybenzimidazole composites. With 20 wt% of f-BNNS loading, the yield and ultimate tensile strengths of f-BNNS/polybenzimidazole composite film can reach ∼225.7 and 252.6 MPa. When the loading of f-BNNS is 30 wt%, the thermal conductivity of f-BNNS/polybenzimidazole composites is ∼8.58 W/mK, 27.68 times higher than that of pure polybenzimidazole. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Novel bioresorbable phosphate glass fiber textile composites for medical applications


A manual bench-top Inkle-type loom was designed to enable hand woven textiles. These phosphate glass fiber (PGF) textiles, along with unidirectional (UD) fiber mats made from the same batch of yarns, were utilized to manufacture fully resorbable textile composites (T-C), unidirectional aligned fiber composites (UD-C), and 0°/90° lay-up UD fiber-reinforced composites (0/90-C). The fiber volume fraction in the composites was set at ∼20%. Retention of flexural properties and mass loss of the composites were evaluated during degradation in phosphate buffered saline (PBS) at 37°C for 28 days. The higher flexural strength and modulus values observed for the T-C when compared to 0/90-C were attributed to the textile weaving resulting in a biased fabric with a higher density of fibers in the warp direction. After 28 days immersion in PBS, ∼20% flexural strength and ∼25% flexural modulus values for the UD-C, T-C, and 0/90-C composites were still prevalent. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Water absorption and mold susceptibility of wood flour/polypropylene composites modified with silane-wax emulsions


Wood plastic composites can absorb water in exterior applications due to the hygroscopicity of wood flour (WF). The cycle of adsorption and desorption process causes damage to the interfacial bonding between WF and polymer matrix, which benefits the fungal attack. In this study, WF was, respectively, immersed with silane, wax emulsion, and their compound systems for modification at different concentrations (1, 2, and 4%, respectively). Then, the modified WF was mixed with polypropylene (PP) to produce WF/PP composites at mass ratio of 6:4. The water absorption and mold susceptibility of the composites against Aspergillus niger were investigated. The results showed that silane can improve the interfacial adhesion between WF and PP. The water uptake of WF/PP composites treated with 4% silane decreased by 6% compared with the control, and the average mold growth rating decreased from level 4 (mold covering of 75–100%) to level 1 (mold covering of 0–25%). The strong hydrophobicity of wax had a negative effect on the interfacial adhesion of the composites. Thus, composites modified with wax and silane-wax compounds showed higher water uptake than the control. However, the mold resistance of composites was improved in these groups. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Densely packed polymer/boron nitride composite for superior anisotropic thermal conductivity


High heat conduction performance of electrical insulating composite is highly desired in thermal management of electronics. In this study, densely packed boron nitride (BN) composites with resin matrices of epoxy, polymethyl methacrylate, and an acrylic copolymer based binder were prepared through a solvent mediated mixing and compression molding method. The solvent mediated mixing assisted homogeneous dispersion; the compression molding removed excessive resin and led to alignment of BN flakes with high filler content. The resulted composites exhibited superior in-plane thermal conductivity k// up to 21.3 W/mK and pronounced anisotropic heat conduction properties. The thermal conductivity was positively correlated with density ρ of a specimen in experimental. A presentation of thermal conductivity k=kρ was proposed, and the dependence of thermal conductivity on specimen density dk(ρ)/dρ > 0 was proven mathematically. The application of BN composite in LED thermal management was demonstrated. An epoxy/BN heat spreader was used to efficiently cool down a 0.3-W LED. The cooling effect was close to that with Al board heat spreader. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Preparation and characterization of bio-based polyurethanes obtained from castor oil and poly (3-hydroxybutyrate) and their nanocomposites


Bio-based polyurethanes (PUs) were synthesized from castor oil (CO) and poly(3-hydroxybutyrate)-diol (PHB-diol) using 1,6-hexamethylene diisocyanate, as nontoxic connecting agent. The PHB content in the obtained PUs was adjusted from 0 to 60.0 wt%. The synthesis was carried out by one pot solution polymerization. PUs nanocomposites loaded with different contents of cloisite®25A (C25A) were prepared by means of in situ solution polymerization. The molecular structure of the obtained PUs was confirmed by FT-IR. The thermal properties of the neat PUs and the resulting nanocomposites were investigated using DSC and TGA. It was found that the cold crystallization of the PHB component was enhanced, while its melt crystallization was retarded with increasing its own content in the PUs. The incorporated C25A in the PU matrix shifted the cold crystallization peak to higher temperature. TGA studies reveal that neat PUs and nanocomposites exhibited three main decompositions steps. The thermal stability of the neat PUs decreased with increasing the PHB content and increased with increasing the C25A content. Tensile mechanical testing revealed that increasing the content of the PHB and C25A made the PUs rigid and strong. The elastic modulus and ultimate tensile strength of the neat PUs were found to increase with increasing the PHB content and enhanced with incorporation of C25A, while the elongation decreased with increasing the PHB and C25A content. The equilibrium swelling in 1,2-dichloroethane decreased with increasing both the PHB and C25A content in PU matrix. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Effects of PAN-based carbon fibers and its precursors on ethylenepropylenediene monomer insulations: Morphology and properties


The properties of ethylenepropylenediene monomer (EPDM) insulations are often inadequate for solid rocket motor (SRM) applications. These materials exhibit relatively high erosion rates during the operation of SRM unless they are reinforced with suitable fiber fillers. In this article, we report the findings of comprehensive mechanical and ablative studies of EPDM insulations blended with polyacrylonitrile (PAN) fiber, pre-oxidized polyacrylonitrile fiber and carbon fiber using a two-roll mill methodology. During the course of this investigation, PAN fiber-filled EPDM insulations showed much superior mechanical and ablative properties than other fiber-filled EPDM insulations. The microstructures of charred layers of these insulations after ablation were characterized by scanning electron microscopy. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Characterization of dimensional stability in flax fiber reinforced polypropylene composites


Flax fibers are a sustainable and high performance reinforcement for polymer composites. Molding polymers and polymer composites nearly always results in warpage or compromised “dimensional stability” of the part. However, there are very few reports on the quantitative analysis of dimensional stability, especially for natural fiber reinforced polymer composites. A systematic study of the dimensional stability of flax fiber reinforced polypropylene (PP) composites is undertaken by measuring the shrinkage of the composites after molding. Shrinkage is directly related to dimensional stability. Using flax fibers decreases part shrinkage or increases dimensional stability. Shrinkage in the molding flow direction is less than shrinkage perpendicular to it, which is shown to be a result of fiber orientation in that direction. Using maleic anhydride modified PP as a coupling agent further decreases the shrinkage. It is found that less shrinkage occurs in composites of higher modulus. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

The roles of surface wettability and roughness of carbon fibers in interfacial enhancement of silicone resin composites


Besides chemical bonding, surface wettability and roughness of carbon fibers (CFs) also play key roles in improving interfacial adhesion of CFs composites. In this study, the roles of surface wettability and roughness of CFs in interfacial enhancement of methylphenylsilicone resin composites were systematically studied. p-Phenylene trimethoxyaminosilane (PTMAS) was chemically grafted onto CFs to increase surface polarity and wettability. Furthermore, by bridging PTMAS, the bigger surface roughness of fibers was obtained after following epoxycyclohexyllsobutyl-polyhedral oligomeric silsesquioxanes (POSS) grafting. PTMAS grafting (CF–PTMAS) had higher wettability and surface energy than that of the grafting with PTMAS and further with POSS (CF–PTMAS–POSS). However, surface roughness of CF–PTMAS was lower than that of CF–PTMAS–POSS. Interfacial shear strength and interlaminar shear strength showed great enhancements, especially for CF–PTMAS–POSS composites, indicating that surface roughness played more important role than the wettability for interface improvement. Additionally, antihydrothermal aging behaviors were also improved obviously. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Evolution of the strain energy release rate during ductile or brittle failure in woven-ply reinforced thermoplastic laminates under high temperature conditions


Depending on laminates’ stacking sequence, the contribution of matrix behavior to the strain energy release rate is evaluated during failure in brittle and ductile composite laminates subjected to high temperature conditions (T > Tg) when matrix toughness is enhanced. The purpose of this work is therefore to investigate the strain energy released along with crack growth in 5-harness satin weave carbon fabric reinforced polyphenylene sulfide (PPS) structures with a Single Edge Notch. The crack growth appears to be self-similar in quasi-isotropic (QI) laminates, and nonself-similar in angle-ply (AP) laminates. Based on fracture mechanics concepts, semianalytical representations of the translaminar failure are combined with an Acoustic Emission (AE) technique to correlate the cumulative AE energy to the strain energy release rate. The experimental results reveal that the fracture toughness increases with increasing precrack length in QI laminates, whereas the effect of increase in precrack length exhibits reduced fracture toughness in AP laminates. The energy released during a non-self-similar crack growth is all the more significant than the stress concentration factor is reduced. A small defect (e.g., precrack) means a larger portion of the mechanical energy brought to the specimen to be dissipated during failure by means of large plastic deformations. With respect to QI laminates, the contribution of PPS matrix toughness to the fracture energy released is more significant in highly ductile AP laminates, resulting in higher fracture toughness. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Effect of nanosize CaCO3 and nanoclay on morphology and properties of linear PP/branched PP blend foams


Branched polypropylene (PP) polymer (BPP), two nanoparticles with different aspect ratios, nano CaCO3, and nanoclay (Cloisite 20A), were used for improving the melt strength of linear PP (LPP) and producing microcellular foam via a solid-state foaming process using supercritical N2 as a physical foaming agent. The effects of BPP and nanoparticles were investigated on the rheological and mechanical properties of the nanocomposite and morphological properties of the foamed samples. The effect of temperature, saturation pressure, and foaming time were studied on the morphological properties of the foams, too. The results showed that the BPP increased the elongation at break of nanocomposite samples, and nano CaCO3 increased tensile strength, elongation at break, and tensile modulus, except at its highest content (15 wt%) and improving the dispersion of nanoclay. The nanoclay improved tensile strength and tensile modulus of nanocomposites, except at its highest content (6 wt%). The nanoclay increased the cell density and reduced the cell size and improved melt strength and cell stability during the foaming process. The nano CaCO3 improved foamability, cell size, and cell density. The simultaneous presence of nanoclay and nano CaCO3 synergistically improved the cell density and decreased the cell size of the foams. The best process conditions were found as 140°C temperature, 80 bar pressure, and 2 h time. The results of the DSC analysis showed that the crystallinity of foamed samples was higher than the nanocomposites and DMTA analysis showed that the tan δ of foamed samples was higher than unfoamed samples. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Processing, characterization, and parametric analysis of erosion behavior of epoxy-LD sludge composites using Taguchi technique and response surface method


Linz-Donawitz sludge (LDS) are the microsized solid particles that are recovered after wet cleaning of the gas emerging from basic oxygen furnace during steel making. This article reports on the development of a new class of thermoset polymer composites filled with this industrial waste called LDS. It includes processing, characterization and solid particle erosion wear of epoxy composites filled with different proportions (0, 5, 10, 15, and 20 wt%) of LDS by solution casting technique. The solid particle erosion wear tests are performed on the prepared epoxy-LDS composite specimens as per ASTM G76 using Taguchi's Orthogonal Arrays followed by the parametric appraisal of the wear process by Response Surface Methodology (RSM). A theoretical model is developed to estimate the erosion rate of these composites under different test conditions. The results obtained from the proposed theoretical model are found to be in good agreement with the experimental values under similar test conditions. Both Taguchi's analysis and RSM suggest that the filler content and the impact velocity are the most significant factors affecting the erosion rate of the composite specimens. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Void content analysis and processing issues to minimize defects in liquid composite molding


This investigation aims to study the impact of key process parameters dealing with the resin impregnation of fibrous reinforcements used in Liquid Composite Molding (LCM). The process parameters are the flow front velocity, the inlet mold pressure and the bleeding flow rate. The experimental setup consists of a computer-assisted injection system and a Resin Transfer Molding (RTM) mold that allows monitoring the progression of the flow front and study the effects of resin bleeding and applying post-fill resin pressure during cure (also known as “mold packing”). Three sets of RTM injections were carried out with a vinyl ester resin and a bidirectional 0°/90° E-glass noncrimp fabrics under (1) constant injection pressure, (2) constant injection flow rate, and (3) bleeding as well as mold packing after filling. The quality of injected parts was evaluated by standard void content analysis based on ASTM burn-off (D2734) tests. The experimental results are consistent with published data and with predictions of the optimal impregnation velocity obtained from capillary rise tests. This study also shows that the impregnation of fibrous reinforcements in LCM can be improved through various injection strategies, namely monitoring of the flow front velocity and specific post-filling procedures. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Processing and properties of short wood fiber/acrylate resin composites


Short wood fibers (SWF) and a water based and formaldehyde free cross linking acrylate resin have been used to produce bulk biocomposites, as a possible material for automotive and friction applications. SWFs of 200–400 µm in length were mixed with the resin in various proportions (40–60 wt%) using a kneading device. The mixture was dried in an oven and later cured in a hot press. Two curing cycles were used for this study: (a) curing at a temperature of 150°C and a pressure of 70 bar and (b) curing at 170°C and a pressure of 80 bar. Various morphological features, flexural and thermal properties, density, and specific wear rate under sliding against smooth steel were examined. Results show that increase in fiber weight fraction led to increase in tensile strength when the material was processed with 170°C and a pressure of 80 bar. Composites with 60 wt% SWF processed with 170°C and a pressure of 80 bar exhibited the highest flexural strength (64 MPa) and flexural modulus (7.2 GPa). Composites processed at lower temperature and pressure (150°C and 70 bar) are found to possess inferior mechanical properties compared with those processed at higher temperature and pressure (170°C and 80 bar). This composite also possessed a nearly stable storage modulus up to 50°C. All composites showed specific wear rate between 10−5 and 10−6 mm3/(Nm) and a very high friction coefficient of μ = 1.25 against smooth steel surfaces. SEM images revealed that there is a very good interfacial adhesion between the fibers and the matrix. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Nanoparticle effects of thermoplastic polyurethane on kinetics of microphase separation, with or without preshear


The present research was carried out in two stages. First, various nanoparticles (Closite30B and multiwalled carbon nanotubes [MWCNTs]) for reinforcement of the polymer matrix were prepared and characterized. Samples were prepared with a melt mixing technique. In the next step, the kinetics of phase separation of thermoplastic polyurethane with nanoparticle (Closite30B, MWCNTs) and preshear were investigated by linear viscoelastic experiments, including frequency sweep and time sweep tests, which were performed on TPU/Closite30B/MWCNT samples varying in nanoparticle content at rheological measurements. The kinetics of phase separation at high preshear and a lower percentage of nanoparticles increased, while they showed a decrease in higher compositions. The nucleation effect of nanoparticles and the effect of preshear with the orientation of the hard segment increases the kinetics of phase separation of the soft and hard segments. The differential scanning calorimetry (DSC) showed that multiple endothermic peaks of thermoplastic polyurethane were affected in the presence of nanoparticles. Dynamic mechanical tests showed that Closite30B has greater affinity with the soft segment and MWCNTs with the hard segment, according to the DSC and rheological experiments. Finally, it was observed that the shear flow and nanoparticles can accelerate phase separation kinetics, but the effect of preshear on the kinetics of phase separation was reduced in the presence of a strong nucleating agent like MWCNTs. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

“Green” composites using bioresins from agro-wastes and modified sisal fibers


“Green” composites were fabricated using modified sisal fibers and agro-waste derived resins from nonedible protein and starch in a simple and cost-effective manner. Sisal fibers were modified using a novel combination of mercerization followed by heat treatment under a pre-determined tension which improved their Young's modulus by over 200% (from 5.5 to 16.7 GPa) and tensile strength by about 50% (from 300 to 450 MPa). The non-edible protein and starch were extracted from defatted karanja (Pongamia pinnata) and mango (Mangifera indica) seed cake wastes, respectively, to prepare the green resins. Composite specimens were fabricated using as-received and modified fibers and agro-waste derived resins using a hand lay-up process followed by hot-pressing. The tensile properties of the composites made with modified fibers showed significant improvement as compared to the composites made with as-received fibers as well as other edible starch or protein-based sisal composites. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Effect of fibre surface treatment on interfacial and mechanical properties of non-woven kenaf fibre reinforced acrylic based polyester composites


The interfacial and mechanical properties of nonwoven kenaf fibre (KF) reinforced acrylic based polyester composites fabricated by resin impregnation process were studied. Different types of treatments were applied to KF, i.e. alkali treatment with NaOH at concentration of 6% (at room and elevated temperature of 60°C) and heat treatment at 140°C for 10h. FT-IR spectral data showed the chemical changes in KF that induced the modification of physical and interfacial characteristics of KF. Alkali treated KF was found to have smaller diameter but higher density. Significant increase in the crystallinity index of treated KF contributed to the improved fibre strength. AFM analysis revealed the exposure of cellulose micro-fibril network and the increase in the area peak density value of treated KF. Surface energy of KF and surface tension of acrylic resin were obtained through Owens–Wendt–Rabel–Kaelble (OWRK) equation and Du Noüy ring approach, respectively, for the interfacial properties determination. The improved wettability of alkali treated KF was confirmed as higher surface energy of the fibre was recorded exceeding the surface tension of acrylic resin, thereby imparting better flexural properties and dynamic mechanical behavior, but conversely deteriorating the fracture toughness of the reinforced composites. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

The effect of eccentricity of load on the behavior of compressed composite columns in critical state


The study concerns a short thin-walled channel section column made of carbon-epoxy laminate. The tested column was subjected to compression, including an eccentric compression force relative to the gravity center of the cross-section of the column toward its higher rigidity. The boundary conditions applied in the study reflected articulated, simple support of the column's ends. The scope of the study included determination of the effect of eccentric load on the structure's buckling mode and critical load. The critical load of the real structure was determined using approximation methods based on the post-critical equilibrium paths of the structure obtained in experimental tests. At the same time, a numerical analysis by the finite element method was performed using the commercial simulation software Abaqus®. The numerical analysis involved solving an eigenproblem to determine the buckling mode of the structure and to determine the critical load of this structure under axial and eccentric load. The experimental results were used to verify the developed numerical models. The analysis enabled determination of the effect of eccentric load on the structure's buckling mode and critical load, which is of vital importance for the design of thin-walled real structures that are coated with reinforcing thin-walled stiffeners. Examples of such constructions include thin-walled stressed-skin structures such as an aircraft's main body section and wings, where the thin skin or outer covering is reinforced by a series of longitudinal profiles with open and closed sections. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Effect of basalt fiber hybridization on the vibration-damping behavior of carbon fiber/epoxy composites


Carbon fiber reinforced polymer composites (CFRPs) have increasingly gained importance among the scientific community as well as industry due to their high specific strength and light weight properties. However, CFRPs suffer from menace of high frequency vibration and low damping ability under normal operating conditions. This study aimed to experimentally investigate the effect of basalt fiber hybridization on vibration damping and tensile properties of carbon fiber/epoxy composites. Interply hybrid composites with varying basalt fiber percentages were fabricated through vacuum assisted resin transfer molding process and the vibration damping properties were evaluated from frequency response curves using half-power bandwidth method. The results showed that incorporation of basalt fiber into the carbon fiber/epoxy composites significantly affected and enhanced damping properties with the increase in volume fraction of basalt fiber content. However, the results from tensile tests displayed significant drops in tensile strength and tensile modulus. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Surface modification of cellulosic materials for polyethylene composite applications


Cellulose fibers obtained from aspen wood via the Organosolv pulping method were surface modified by maleated polyethylene (MAPE) in a xylene solution to improve their adhesion/dispersion in 30% wt. filled linear medium density polyethylene composites. The chemical analysis of unmodified and modified fibers as well as morphological, rheological, and mechanical characterizations of their composites showed that successful MAPE grafting on the fibers' surface was achieved leading to a substantial improvement of the fiber-matrix interfacial quality as tensile strength improved by 29% when compared with the composites containing unmodified fibers. The treatment also improved the rigidity and creep resistance of these composites which is highly suitable for building and construction applications. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Development of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/boron nitride bionanocomposites with enhanced barrier properties


This research aims at improving barrier properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, by incorporating boron nitride particles (BNPs) via melt compounding. To meet this objective, PHBV nanocomposite samples containing different BNPs were prepared and the effects of BN loading and silane surface modifier on the barrier properties of PHBV nanocomposites were investigated. For all the nanocomposite samples, the permeability is decreased in comparison to the neat PHBV due to both the presence of BN particles and a higher crystallinity. The results demonstrate that barrier properties of the composites were found to increase more for the silanized flake type BN (OSFBN) compared to silanized hexagonal disk type BN (OSBN). The best barrier properties are obtained for the nanocomposite sample containing 2 wt% OSFBN, for which a reduction of oxygen permeability up to 36% was observed in comparison to the neat PHBV. Silane-treated BN nanoparticles yielded nanocomposites characterized by good barrier performance and fine BN dispersion, as shown by SEM investigations. The phenomenological gas permeation models were employed to evaluate the effect of BN particles on oxygen transmission properties. The best approach was found for the relative permeation by using Cussler and Lape models. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Potential of magnetite reduced graphene oxide/chitosan nanocomposite as biosorbent for the removal of dyes from aqueous solutions


In this study, the fast and considerable adsorption of Remazol Black B (RBB) and Acid Red 22 (AR22) from an aqueous solution by magnetite reduced graphene oxide (rGO)/chitosan nanocomposite was studied. Several important parameters influencing the adsorption of dye pollutants such as pH (1–8), sorbent mass (5–25 mg), contact time (30–180 min), and dye concentration (10–50 ppm) were considered. The results showed that, the surface property of rGO, the amino, and hydroxyl functional groups of chitosan, and the magnetic property of Fe3O4, the adsorbent possesses quite good adsorption capacity to the dye under investigation. Both dye solutions sorption on nanocomposite was strongly dependent on pH. An adsorption efficiency of 95.32 and 99.46% could be achieved at initial RBB and AR22 concentrations of 20 mg/mL, respectively. In the aqueous solution of RBB and AR22, the adsorption data could be fitted by the Langmuir and Freundlich equations, respectively. In addition, the adsorption kinetics of RBB and AR22 were investigated to show that it was well-described by Elovich and Blanchard models, respectively. These results indicate that magnetite reduced GO/chitosan nanocomposite could be regarded as a potential biosorbent for RBB and AR22 dye removal in wastewater treatment process. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Crashworthiness characteristics of carbon–jute–glass reinforced epoxy composite circular tubes


This article provides an experimental investigation into the crashworthiness of carbon–jute–glass reinforced epoxy circular composite tubes. The test specimens were fabricated of 6 layers with different stacking sequence using wet-wrapping process and tested under uniaxial quasi-static compression loading up to complete crushing. The effects of hybrid reinforcement, stacking sequence, and relative reinforcement amounts on the energy absorption capabilities and failure modes were studied. Also, the crush load–displacement response, initial crushing failure load, total energy absorption, specific energy absorption, average crushing load, and crushing force efficiency were determined and discussed. The scanning electron microscope study was considered to analyze the failure modes of the crushed specimens. Results indicate that specimens' failure modes and energy absorption capabilities were highly dominated by the reinforcement combinations and plies stacking sequence. Also, hybrid carbon–jute–glass reinforced epoxy composite tubes have the potential to be used as energy absorbers as compared to jute-reinforced epoxy composite tubes. The JGC composite tube has a higher load carrying capacity and energy absorption capability compared to other hybrid composite tubes, so it seems to be the best appropriate choice for energy absorbing devices. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Modeling and optimization of tensile strength and modulus of polypropylene/kenaf fiber biocomposites using Box–Behnken response surface method


The aim of this work includes modeling and optimization of the tensile properties of natural fiber biocomposites using the concept of experimental design. A three-factor, three-level Box–Behnken design, which is subset of the response surface methodology (RSM), has been applied to present mathematical models. The effect of three independent variables; kenaf fiber load, fiber length and polypropylene-grafted maleic anhydride (PP-g-MA) compatibilizer content have been investigated on the tensile strength and modulus of polypropylene/kenaf fiber/PP-g-MA biocomposite. These models can be used as an interesting method for analytically evaluating both the tensile strength values and their corresponding tensile modulus as function of independent variables. The optimization results, obtained using the optimization part of Design-Expert Software, showed that the most optimal tensile strength and tensile modulus were to be 32.70 MPa and 2,182.33 MPa, respectively; and achieved at 28.95 wt% of the kenaf fiber, fiber length of 6.22 mm and PP-g-MA content of 5 wt%. The obtained R2 values and normal probability plots indicated a good agreement between the experimental results and those predicted by the model (above 0.95 for all the responses). Moreover, the tensile modulus of the biocomposite was analyzed by means of micromechanical models. The performance of the Halpin–Tsai and Cox–Krenchel models in predicting the tensile modulus of biocomposites was compared with available experimental results. In addition, the fracture surface morphologies and wettability of the samples were investigated by scanning electron microscopy (SEM) and contact angle measurement, respectively. It was found that the fiber load and PP-g-MA compatibilizer content play a significant role in the tensile properties and morphology of the biocomposites, as proven by SEM and contact angle measurement. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Role and sinergy of block copolymer and carbon nanoparticles on toughness in epoxy matrix


In this work, the relations between fracture surface roughness in mode I and the content of different carbon nanoparticles, graphene nanoplatelets (GNP) and carbon nanotubes (CNT) were systematically investigated. A block copolymer (BC) was also used to aid the dispersion process considering its role on fracture toughness. Both KIc and GIc were found to increase significantly with the addition of a BC along with carbon nanoparticles. Roughness measurements showed that the value of surface roughness (Ra) does not depend on the toughness, and decreases as the precrack distance increases. In the system with the greatest amount of graphene (0.5 wt%), the agglomerates impaired the material's tenacity and crack deflection with GNP delamination as the fracture mechanism. As for the CNT/epoxy nanocomposites with the BC, strong adhesion between matrix and nanotubes prevented debonding, so the CNTs break, rather than pulling out, after crack bridging, the so called sliding-fracture mode failure. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Issue Information - Table of Contents


Comparison of natural halloysite with synthetic carbon nanotubes in poly(lactic acid) based composites


The objective of this study is to compare the mechanical properties, structure and degradability of the nanocomposites prepared with tubular nanofillers, halloysite (HNT) and carbon nanotube (CNT) in poly(lactic acid) (PLA), and thermoplastic polyurethane (TPU) toughened PLA (T-PLA) matrices. In the PLA matrix, CNT increased, whereas HNT decreased the tensile strength with increasing filler content. Also, the elongation at break and impact strength decreased with increasing CNT content, but these properties were relatively unchanged with increasing HNT content. However, when (TPU) was used as an impact modifier-compatibilizer, addition of HNT further increased the impact strength and the elongation at break of the matrix, since short and straight HNT fibers were pulled out from the extensible, toughened matrix. The long and curvy CNT fillers always caused brittle fracture and affected the impact strength and elongation at break in a negative manner as the CNT content was increased. Both types of fillers did not significantly influence the degradation of PLA or toughened PLA matrices. POLYM. COMPOS., 38:2337–2346, 2017. © 2015 Society of Plastics Engineers

Effects of silane coupling agents on tribological properties of bentonite/nitrile butadiene rubber composites


In this work, effects of silane coupling agents on the tribological properties of bentonite/nitrile butadiene rubber (NBR) composites were investigated. The composites were fabricated with a facile method. Three silane coupling agents, (3-mercaptopropyl)trimethoxysilane (MPTMS), bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) and [3-(2-aminoethylamino)propyl]triethoxysilane (AEAPTMS) were employed in our research. The short sulfur bonds formed between MPTMS and macromolecules in the matrices limited the extension of the contact interface between rubber matrices and glass plate, which contributed to the reduction in friction coefficient. With TESPT and AEAPTMS, the adhesion force of the composites was remarkably reinforced, further leading to the increase in friction coefficient. In the wear test, bentonite/silane/NBR composites showed better wear resistance compared to the specimens fabricated without silanes. By investigation on the morphological features of the worn surfaces, different wear mechanisms for composites with/without silane coupling agents were illustrated in detail. Generally, the effects of silanes to adhesion force, hysteresis loss ratio, and hardness all contributed to the friction coefficients of the composites. In wear test, the effects of the silanes on hysteresis force were prominent. Incorporated with MPTMS, the composite showed poor wear resistance due to its high hysteresis loss ratio. POLYM. COMPOS., 38:2347–2357, 2017. © 2015 Society of Plastics Engineers

Effect of coupling agent on crystallization and rheological properties of poly(ethylene terephthalate) composite masterbatches


Poly(ethylene terephthalate)/carbon black/coupling agent composite masterbatches were fabricated using separate feeding technique. The effect of coupling agent on crystallization of composite masterbatches was investigated by differential scanning calorimetry, wide-angle X-ray diffraction, and Fourier transform-infrared spectroscopy, respectively. The results show that the strong interfacial interaction among poly(ethylene terephthalate) (PET), coupling agent and carbon black hinders chains mobility in process of PET crystallization, which is illustrated by interfical structure model. Whereas, the crystallinity of composite masterbatch increases due to uniform dispersion of carbon black modified by coupling agent. Activation energy of viscous flow of the composite masterbatches is closer to that of virgin PET, so the spinning parameters can be controlled according to each other. Besides, structural viscosity index of composite masterbatches is greater due to strong interfacial interaction among PET, coupling agent and carbon black. Thus, in order to smooth spinning, the composite masterbatches need greater shear rate compared with PET/carbon black masterbatch. POLYM. COMPOS., 38:2358–2367, 2017. © 2015 Society of Plastics Engineers

Analyzing three-dimensional structure and geometrical shape of individual cellulose nanocrystal from switchgrass


The three-dimensional morphology, size distribution, and structure of individual cellulose nanocrystals (CNCs) isolated from switchgrass (Panicumvirgatum L), a representative raw biomass material, were investigated in this research. Width and height evolutions along the individual CNC longitudinal direction were statistically and quantitatively characterized using transmission electron microscopy (TEM) and atomic force microscopy (AFM). Lognormal distribution was identified as the most likely for cellulose nanocrystals’ size distribution. Height and width dimensions were shown to decrease toward the ends from the midpoint of individual CNCs, implying a spindle shape. The observed rough surfaces of CNCs were explainable as the results of acid etching of the subcrystalline and disordered region located at the surface. X-ray diffraction analysis of crystallite size accompanied with TEM and AFM measurements revealed that the cross-sectional dimensions of individual switchgrass CNC were either rectangularly or elliptically shaped, with an approximately 3–5 nm lateral element length range. POLYM. COMPOS., 38:2368–2377, 2017. © 2015 Society of Plastics Engineers

Preparation of expandable graphite and its flame retardant properties in HDPE composites


This study showed an efficient and novel way to prepare expandable graphite (EG) which is one kind of halogen-free flame retardant using the O3-hydrothermal process. The results showed the expanded volume of EG using the O3-hydrothermal process was higher than those compared to convectional liquid phase synthesis, ultrasound irradiation and hydrothermal method. X-ray diffraction pattern, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to analyze the structure and confirm that EG had been prepared. Scanning electron microscope was utilized to observe the morphology of EG and char from HDPE/O3-HEG composites. Cone calorimeter, limiting oxygen index, and UL-94 were used to investigate the flame retardant property of the HDPE/O3-HEG composites and showed the HDPE/O3-HEG composite possesses excellent flame retardant property. POLYM. COMPOS., 38:2378–2386, 2017. © 2015 Society of Plastics Engineers

Evaluation of Kraft lignin as natural compatibilizer in wood flour/polypropylene composites


This study investigated the effect of Kraft lignin as natural compatibilizer on the water absorption, thermal, mechanical, and interfacial properties of poplar wood flour (WF)/polypropylene (PP) composites. Varying contents (0.5, 1, 2, 4, and 8 wt%) of lignin were added to WF and PP by direct mixing, then the composites were prepared by two-screw extrusion and compression moulding. Results showed that lignin incorporation reduced the water absorption and postponed the thermal decomposition of the composites. Composites with lower lignin contents (0.5% and 1%) could get the optimal properties, and the excess lignin contents (4% and 8%) resulted in slight decrease in the mechanical properties. DMA and calculation of adhesion factor showed that the composites with 0.5% lignin had the best interaction between WF and PP. The morphologies of fractured surface also indicated improved interfacial adhesion between WF and PP from the addition of 0.5% and 1% lignin. POLYM. COMPOS., 38:2387–2394, 2017. © 2015 Society of Plastics Engineers

Electrochemical properties of a highly biocompatible chitosan polymer actuator based on a different nanocarbon/ionic liquid electrode


Ionic actuators have attracted attention due to their remarking large strain under low-voltage stimulation. Because the actuation performance is mainly dominated by the electrochemical and electromechanical processes of the electrode layer, the electrode materials and structure are crucial. In this manuscript, we report a highly biocompatible polymer actuator, which consists of multiwalled carbon nanotubes (MCNTs) film as double electrode layer and an electrolyte layer equipped with a chitosan polymer skeleton and an ionic liquid. The electrochemical properties of chitosan polymer actuator under various content of MCNTs were presented by SEM, cyclic voltammetry, and alternate current impedance. Results represented that MCNTs as a reinforcing agent in the chitosan polymer actuator strongly affected the electromechanical energy efficiency. POLYM. COMPOS., 38:2395–2401, 2017. © 2015 Society of Plastics Engineers

Investigation of mechanical properties of porous composite scaffolds with tailorable degradation kinetics after in vitro degradation using digital image correlation


Tissue engineering combines artificial scaffolds and living cells in order to reconstruct damaged tissues and organs. The biodegradable scaffolds should maintain their mechanical properties during first stages of the regeneration. The aim of this study was to investigate the extent the degradation affects the mechanical stability of novel biodegradable composite scaffolds in relation to their composition. The scaffolds were made using fused deposition modeling. They were composed of ternary composites containing poly(ε-caprolactone) (PCL), 5 wt% of tricalcium phosphate (TCP) and 5, 15, and 25 wt% of poly(lactide-co-glycolide) (PLGA). Scaffolds made of pristine PCL and binary composite PCL–TCP were tested as reference samples. The degradation experiment was carried out in simulated body fluid at 37°C for 12 weeks. Mechanical tests were carried out in a mechanical tester. Strain was measured using digital image correlation and crossbar displacement. Chemical composition had a significant effect on initial mechanical properties and their changes during degradation. The initial apparent Young's modulus of ternary composite scaffolds was two times higher than that of PCL–TCP. Higher PLGA concentration yielded faster decrease of the mechanical properties. At the end of the experiment, there were no significant differences of the modulus among all tested materials although degradation of the ternary composite scaffolds was significantly advanced. POLYM. COMPOS., 38:2402–2410, 2017. © 2015 Society of Plastics Engineers

Automation of the vacuum assisted resin transfer molding process for recreational composite yachts


The use of glass fiber reinforced plastics (GFRP) in large primary marine structures has noticeably increased due to their favorable stiffness, strength, durability, and manufacturability. However, GFRP construction can become cost-prohibitive at the superyacht-scale (36–60 m) as defects and labor intensiveness increase. In this paper, we presented an automated vacuum assisted resin transfer molding process (VaRTM) that can be integrated into an existing setup for manufacturing recreational composite yachts in the 49-meter range. The objective of automating the system is to reduce defects and labor intensity. The developed automation system consisted of a controller, resin supply lines with valves, and infrared sensors. The control software, valves and sensors were custom developed. The system automatically monitors and adjusts resin flow in the mold in real-time to mitigate flow front variations. The system was used to run three different scenarios common in marine composites manufacturing using VaRTM; a flat plate with consistent ply sequence, a flat plate with varying ply sequence, and a scaled yacht keel section. Results indicated that use of the automated setup improved overall evenness of resin flow and limited unwanted convergence compared to the traditional manual setup. Tensile testing indicated similar mechanical performance but greater variation in the manual sample. Voids were discovered in regions of flow convergence of the manual panel and reflected slightly more varied tensile properties as compared to automated panels. POLYM. COMPOS., 38:2411–2424, 2017. © 2015 Society of Plastics Engineers

Mechanical properties of carbon fiber composites modified with graphene oxide in the interphase


The surface topographies of carbon fibers treated by sizing agents with different graphene oxide (GO) content were investigated by scanning electron microscopy. The surface elements compositions of carbon fibers were determined by X-ray photoelectron spectrometer. The interfacial properties of composites were studied by interfacial shear strength. The thermo-mechanical properties of two typical specimens (CF-G0 and CF-G1 composites) were investigated by dynamic mechanical thermal analysis. The results showed the introduction of GO sheets on carbon fibers surfaces effectively improved the mechanical properties of carbon fibers/epoxy composites. POLYM. COMPOS., 38:2425–2432, 2017. © 2016 Society of Plastics Engineers

Melt extrudate swell behavior of multi-walled carbon nanotubes filled-polypropylene composites


The extrudate swell behavior of polypropylene (PP) composite melts filled with multi-walled carbon nanotubes (MWCNTs) was studied using a capillary rheometer in a temperature range from 190 to 230°C and at various apparent shear rates varying from 50 to 800 s−1. It was found that the values of the extrudate swell ratio of the composites increased nonlinearly with increasing apparent shear rates, while the values of the extrudate swell ratio decreased almost linearly with increasing temperature. The values of the melt extrudate swell ratio increased approximately linearly with increasing shear stress, while decreased approximately nonlinearly with an increase of the MWCNT weight fraction. In addition, the extrudate swell mechanisms were discussed with observation of the fracture surface of the extrudate using a scanning electronic microscopy. This study provides a basis for further development of MWCNTs reinforced polymer composites with desirable mechanical and thermal properties. POLYM. COMPOS., 38:2433–2439, 2017. © 2015 Society of Plastics Engineers

High performance PP/SEBS/CNF composites: Evaluation of mechanical, thermal degradation, and crystallization properties


Nanocomposites comprising carbon nanofibers (CNF) were prepared and evaluated in terms of morphology, mechanical performance, thermal stability and crystallization properties. It was found that addition of CNF reinforced polypropylene (PP) matrix by marginally increasing the strength and modulus, but at the expense of toughness and ductility. To improve the toughness of the composites, polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) was used. Presence of SEBS remarkably improved the toughness and ductility of the composites. The optimum level of reinforcement was observed at 0.1 wt% of CNF in the composites. Phase morphology studies revealed that at this concentration, CNF were well dispersed in polymer phases and beyond it, agglomeration occurred. PP/SEBS/CNF (0.1 wt%) nanocomposites exhibited good strength, excellent toughness and decent modulus, which make them suitable for cost effective, light-weight, tough and stiff material for engineering applications. It was observed that thermal stability of composites is only marginally improved whereas crystallinity of PP drastically reduced by the addition of CNF. POLYM. COMPOS., 38:2440–2449, 2017. © 2015 Society of Plastics Engineers

Grafting polystyrene with various graft densities through epoxy groups of graphene nanolayers via atom transfer radical polymerization


A double bond and amine group containing chemical (OD) was synthesized by coupling reaction of ethylenediamine and 3-(chlorodimethylsilyl)propyl methacrylate. Subsequently, graphene oxide (GO) was functionalized with OD in different densities via ring opening of its epoxy groups. The graphene containing double bond (GOD) was incorporated into polystyrene (PS) chains by a grafting through atom transfer radical polymerization. Grafting of OD at the surface of GO was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). The interlayer spacing of the graphenes was evaluated by X-ray diffraction. Molecular weight and PDI values of the free and attached PS chains were studied by size exclusion chromatography. TGA was also used to study the degradation points, char values, and grafting ratios. Relaxation of PS chains in the presence of graphene layers was evaluated by differential scanning calorimetry. Scanning electron and transmission electron microscopies show that flat graphene layers are wrinkled during oxidation and functionalization processes. POLYM. COMPOS., 38:2450–2458, 2017. © 2015 Society of Plastics Engineers

Concrete beams strengthened with prestressed unbonded carbon-fiber-reinforced polymer plates: An experimental study


This study addresses the applicability and effectiveness of prestressed unbonded carbon-fiber-reinforced polymer (CFRP) for strengthening concrete beams. Three- and four-point flexural tests were conducted up to failure for 10 concrete beams. The cracking, yield, and experimental nominal loads of the prestressed strengthened beams increased with the prestress levels. However, the ultimate loads were similar regardless of the prestress level because beam failure was dominated by rupture of the CFRP plates. Based on the results, the recommended appropriate prestress level for securing the ductility of a prestressed strengthened beam is ≤40% of the tensile strength of the CFRP plate. POLYM. COMPOS., 38:2459–2471, 2017. © 2015 Society of Plastics Engineers

Effect of plasticizer on the electrical, thermal, and morphological properties of carbon black filled poly(propylene)


Poly(propylene) (PP)/carbon black (CB) composites are melt-blended in a Brabender mixer with varying CB content. With the special-grade conductive CB, the surface resistivity of PP/CB composite was reduced by 13 orders of magnitudes by increasing the CB content from 0 to 15 wt%. The plasticizer poly(ethylene glycol) di-methyl ether (PEGDME) is used (0–5 wt%) to improve the dispersion of the CB in the polymer matrix and to reduce the surface resistivity of the composites. But the PEGDME plasticizer used here has no positive effect on the surface resistivity of the composites; in fact, it enhances the surface resistivity value by one order of magnitude at higher concentration (5 wt%). The scanning electron microscopy (SEM) pictures indicate that the presence of foreign material (plasticizer) especially at higher concentration disrupts the continuous carbon network inversely affecting the conductivity values. Finally, the optimization of the input variables (CB and PEGDME loading) is done using the design of experiment approach. POLYM. COMPOS., 38:2472–2479, 2017. © 2015 Society of Plastics Engineers

Magnetic composites prepared by incorporation of strontium ferrite into polar and non-polar rubber matrices


Strontium ferrite was incorporated into different rubber matrices to prepare rubber magnetic composites. Three types of elastomers, butadiene rubber BR as non-polar elastomer, acrylonitrile butadiene rubber NBR and blend acrylonitrile butadiene rubber–polyvinyl chloride NBR/PVC as polar elastomers were chosen as rubber matrices. Surface modified strontium ferrite as magnetic filler was applied in concentration scale ranging from 0 to 100 phr. Besides the rubber and the filler, the rubber compounds contained only the ingredients of sulfur curing system. The results revealed that thermo-physical and magnetic properties of composites increased with doping content of ferrite. Moreover, the improvement of mechanical properties in dependence on strontium ferrite content was also recorded. It can be stated that the improvement of composite properties is in close correlation with the increase of polarity of the rubber matrix. POLYM. COMPOS., 38:2480–2487, 2017. © 2015 Society of Plastics Engineers

Comparison of experimental and modeling results for cure induced curvature of a carbon fiber laminate


The use of carbon fiber laminated structures has steadily grown in industrial use during recent decades where the part performance is a function of both the manufacturing process and the underlying constitutive materials. This work presents an approach to predict the part geometry and internal stress state from experimentally characterized constitutive properties due to the manufacturing cure cycle. Our predicted results for the internal stress state are in agreement with that of previous published works, and the predicted part deformations agree with the experimental results for both of the fiber packing densities investigated. The uniqueness of this work is in the aspect of using basic micromechanical models to determine the dependence of the lamina behavior on the structural and thermal constitutive properties of an individual fiber and the surrounding polymer matrix. A full three-dimensional (3D) FEA model is constructed with spatially varying properties obtained from the predicted lamina properties. The study models the cooling aspect of part fabrication after cure has been completed and the furnace temperature has dropped below the polymer's glass transition temperature. A discussion is provided at the end for the limitations of the approach and also where additional work would be needed to extend this approach to a physical system that does not follow the epoxy system investigated. POLYM. COMPOS., 38:2488–2500, 2017. © 2015 Society of Plastics Engineers

Effect of thermoplastic veils on interlaminar fracture toughness of a glass fiber/vinyl ester composite


The effects of two thermoplastic micro-veils, polyamide (PA) and polyethylene terephthalate (PET) veil, on the interlaminar fracture toughness of a glass fiber/vinyl ester (GF/VE) composite were investigated. The veils incorporated into the composite as interleaving materials were first characterized via scanning electron microscopy (SEM), differential scanning calorimetry (DSC), contact angle and tensile testing in order determine the best candidate as toughening agent for the GF/VE composite. Composite laminates were manufactured by vacuum-assisted resin infusion process. Double cantilever beam (DCB) testing was performed to investigate the Mode I type interlaminar fracture toughness of the composites, which was characterized by critical strain energy release rate (GIC). An increased GIC was obtained by incorporating the PA veil, but it changed negligibly by the addition of the PET veil. The analysis of the composites fracture surface via SEM revealed increased fiber bridging between adjacent plies in the case of PA veil interleaved composites which played a key role in enhancing the Mode I interlaminar fracture toughness. However, the PET veil present in the interlaminar region did not take part in any energy absorbing mechanism during the delamination, thus keeping the GIC of the composite unaltered. POLYM. COMPOS., 38:2501–2508, 2017. © 2015 Society of Plastics Engineers

The composition and ageing of high-viscosity and elasticity asphalts


Different kinds of plasticizers and crosslinkers were used to prepare high-viscosity modified (HVM) asphalt and high-elastic modified (HEM) asphalt and the major physical properties were studied and compared. The kinds of plasticizers were optimized and the difference in composition between HVM and HEM asphalts was clarified. The plasticizers with different thickness and flexibility were available for HVM or HEM asphalts respectively. The kinds of crosslinkers were also compared and optimized and it was found that the most effective crosslinker was sulfur. The effect of anti-ageing reagent on HEM asphalt was confirmed and it was found that one of the most effective way to retain the properties of HVM and HEM asphalt before ageing was to increase the SBS content further. POLYM. COMPOS., 38:2509–2517, 2017. © 2015 Society of Plastics Engineers

Effect of fiber chemical treatment of nonwoven coconut fiber/epoxy composites adhesion obtained by RTM process


In this work untreated and alkali treated nonwoven coconut fiber mats/epoxy resin composites were manufactured using the resin transfer molding process. The alkaline solution removes some impurities present on fibers superficial layers and the effect regarding fiber/matrix adhesion were investigated by thermogravimetric analysis, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), ultrasonic C-scan, and quasi-static flexural test. Results show a removing of some amorphous fibers constituents, mainly waxes, extractives, and hemicellulose, revealing the fiber roughness surface but no initial degradation temperature changing. Regarding the composites, a similar interfacial adhesion was observed in both one through the results of SEM, DMA and quasi-static flexural tests. The conclusion is that chemical treatment conditions applied on the fiber surface was been suitable to improve fiber roughness but did not the adhesion between coconut fibers mat and epoxy resin. POLYM. COMPOS., 38:2518–2527, 2017. © 2015 Society of Plastics Engineers

Mechanical performance of woven carbon fabric reinforced pCBT composites with nanosilica particles


The effect of nanosilica content (0, 0.5, and 2 wt%) on mechanical performance of carbon fabric woven cloth reinforced polymerized poly(butylene terephthalate) resin composites (CF/pCBT) is investigated. The catalyst and nanosilica particles are added on the prepreg surface, and hot-press processing is adopted in order to manufacture CF/pCBT composites. The experimental results reveal that nanosilica could enhance the mechanical performance of CF/pCBT composites. After adding nanosilica in the composites, elastic modulus enhances 23.96%, and Mode-II fracture toughness increases 380.43%. Scanning electron microscope observation shows that dispersity of nanoparticles in composites plays an important role on the overall mechanical performance of the obtained composites. Furthermore, failure mechanism has been analyzed according to the damage morphology. POLYM. COMPOS., 38:2528–2535, 2017. © 2015 Society of Plastics Engineers

Modeling analysis of fiber hybridization in hybrid glass/carbon composites under high-velocity impact


The effects of fiber hybridization on damage behavior of hybrid glass/carbon composites under high-velocity impact were investigated. The Hashin damage model is adopted to model the damage initiation of composites, and the bilinear form of damage evolution law based on the effective displacement is employed. The numerical results show a reasonable agreement with the experimental data. The residual velocity of impact projectile is approximately shown a linearly decreasing trend with the increasing of the thickness of glass fabric ply. As the proportion of glass fabric ply in the hybrid laminates increases, the impact resistance of laminates increased gradually. POLYM. COMPOS., 38:2536–2543, 2017. © 2015 Society of Plastics Engineers

Recycling carbon fiber from composite waste and its reinforcing effect on polyvinylidene fluoride composite: Mechanical, morphology, and interface properties


Recycled carbon fiber (RCF) was reclaimed from thermoset composite waste and employed as reinforcement from 0 to 30 wt% to prepare polyvinylidene fluoride (PVDF)/RCF composite. Commercial virgin carbon fiber (VCF) was used as comparison. The surface morphology, chemistry, and tensile properties of carbon fibers were investigated by Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and tensile test. Results showed that the roughness, O/C ratio and –COO content of RCF surface were significantly improved after recycling. In addition, the single fiber tensile strength and modulus of RCF was lower than that of VCF. The interfacial adhesion between RCF and PVDF was much stronger due to the high chemical activity and roughness over the RCF surface. Mechanical properties of composites were investigated by flexural test, impact test, and Dynamic Mechanical Analysis (DMA). It is found that the PVDF/RCF composite showed higher flexural properties, storage modulus, and lower impact strength, which indicated the strong interfacial adhesion, played an important role in reinforcing. The morphology of fracture further demonstrated the strong interface in PVDF/RCF composite. The fiber length distribution and crystallinity of composites were also evaluated to characterize the composites. The work develops potential for recycling and reuse of carbon fiber, and also expands the application of PVDF based composite. POLYM. COMPOS., 38:2544–2552, 2017. © 2015 Society of Plastics Engineers

Review of the applications of biocomposites in the automotive industry


The article provides an overview of biocomposite application in the automotives via a documentation of their history, chronology and progressive steps taken to break into the production lines of a number of key auto makers. It offers a detailed analysis of the key factors that have motivated the research and subsequent adoption of biocomposites; taking a peek at the advantages, disadvantages, and challenges experienced in the process. Auto makers and parts suppliers that have been a force behind this campaign, have also been accorded a fair share in the article. Future projection of role of these materials in the industry; with the ideas well dressed in form of bio concept cars caps up the paper. Automotive refers to; passenger cars, sport utility vehicles, vans, trucks, buses, and recreational vehicles. POLYM. COMPOS., 38:2553–2569, 2017. © 2016 Society of Plastics Engineers

Processing and characterization of a polylactic acid/nanoclay composite for laser sintering


In this work, the feasibility of processing polylactic acid (PLA) and a PLA/nanoclay composite by laser sintering (LS) were investigated. The morphology of both the PLA and PLA/nanoclay powder was examined by scanning electron microscopy. LS process parameters, especially powder bed temperature, laser power, and laser scan count were studied. The effect of the addition of nanoclay on the thermal and flexural properties of LS PLA parts was examined. The results showed that PLA/nanoclay required a lower processing powder bed temperature compared with neat PLA. Under the same powder bed temperature, PLA/nanoclay parts exhibited an improvement in flexural modulus compared with neat PLA. Flexural modulus was increased significantly with double scan for both neat PLA and PLA/nanoclay LS parts. POLYM. COMPOS., 38:2570–2576, 2017. © 2015 Society of Plastics Engineers

Characterization, morphology, and biodegradation of bioplastic fertilizer (BpF) composites made of poly(Butylene succinate) blended with oil palm biomass and fertilizer


Poly(butylene succinate) (PBS) is a versatile biodegradable polymer that can be processed into slow-release bioplastic fertilizer (BpF) composites using twin screw extruder extrusion method, with controlled formulation and temperature. In this study, slow-release BpF composites were created by blending NPK fertilizer with biodegradable plastic composites and oil palm biomass. Temperature processing was done at 125°C–145°C for 3–5 min using twin screw extruder. Its thermal degradation occurred initially at 263.44°C and reached maximum at 300.73°C. In biodegradation test, the weight losses of PBS/NPKC1 and PBS/NPKC2 were about 60% while the weight losses of PBS/EFB/NPKC1 and PBS/EFB/NPKC2 were 72.68% and 73.09%, respectively. It was observed under scanning electron microscope that PB1 and PB2 showed more homogeneous adhesion and better wetting of PBS. POLYM. COMPOS., 38:2577–2583, 2017. © 2015 Society of Plastics Engineers

Electrical properties of polyimide composite films containing TiO2 nanotubes


A study on the dielectric behavior of polyimide composite films containing different amounts of TiO2 nanotubes (TNs) was performed. The films were prepared by casting solutions resulting from direct mixing of a poly(amic acid) and TNs onto glass plates, followed by thermal imidization. The influence of TNs content on the properties of polyimide composites was investigated. AFM and SEM analyses showed good compatibility between the filler and polymer matrix. Dynamic mechanical analysis and broadband dielectric spectroscopy were used to evidence relaxation processes into the films. The electrical properties were evaluated on the basis of dielectric constant and dielectric loss, and their variation with frequency and temperature. At moderate temperature a secondary β relaxation was observed while incorporation of TNs decreased the activation energy and facilitated the appearance of an additional β1 process. An α relaxation and a conductivity process were evidenced at higher temperatures. The values of dielectric constant and dissipation factor increased with TNs amount, and the maximum of σ relaxation peak shifted to higher temperatures. POLYM. COMPOS., 38:2584–2593, 2017. © 2015 Society of Plastics Engineers

Fabrication and characterization of rice bran carbon/styrene butadiene rubber composites fabricated by latex compounding method


Novel rice bran carbon (RBC) filled styrene butadiene rubber (SBR) composites were fabricated by latex compounding method (LCM). The chemical structure determination and the static precipitation experiments definitely authenticated the hydrophilicity of RBC, which enables RBC to be uniformly dispersed in water without surface modification and thereby compounded with rubber latex directly. The SBR/RBC composites prepared by LCM exhibited homogeneous filler dispersion state and superior mechanical properties compared with those compounded by solid compounding method (SCM). The vulcanization properties, mechanical properties, thermal stabilities, and swelling properties of SBR/RBC composites prepared by LCM were studied. It was revealed that the tensile strength, modulus, and tear strength of SBR/RBC composites increased correspondingly as the RBC loading increased from 0 to 80 phr. The decomposition temperature would stop rising when the filler loading exceeded 40 phr. The significant increases of the crosslink density with increasing filler volume content indicated the reinforcement effect of RBC. POLYM. COMPOS., 38:2594–2602, 2017. © 2015 Society of Plastics Engineers

Investigation of the high velocity impact behavior of grid cylindrical composite structures


In this paper, the experimental behavior of grid cylindrical composite structures, which are used widely in engineering structures, under ballistic impact is investigated. For this purpose, some grid cylindrical composite specimens were manufactured by the filament winding process and perforated by projectile using the ballistic gas gun. Incident impact velocity and exit velocities of projectile were recorded in each test. The results show that the presence of the ribs prevents pervading of damaged area of one cell to its adjacent cells. The structure behaves differently against projectile with velocity near ballistic limit and higher velocities. The results demonstrated that, by getting close to the ribs location, ballistic limit velocity was increased. However, due to reduction in energy absorption mechanisms in grid composite structures which are impacted in higher velocity than ballistic limit, projectile was exited of grid samples at higher velocity than unstiffened composite shells. Also, investigation of delamination in composite shell and ribs, debonding between ribs and shell (or separation of ribs and shell), residual velocity of projectile, damaged area of the grid specimens and the effects of curvature in two different velocities are presented and the results are discussed. POLYM. COMPOS., 38:2603–2608, 2017. © 2015 Society of Plastics Engineers

Investigation of the compaction behavior of carbon fiber NCF for continuous preforming processes


This paper describes the experimental investigation of the compaction behavior of dry single-ply and multi-ply fabric stacks (preforms). Utilizing four biaxial (two 0°/90° and two ±45°) and one triaxial (0°±45°) carbon fiber NCF, differing in weight (300 g/m2, 600 g/m2) and type of stitching (tricot, pillar, hybrid), the influence of compaction speed, pre-compaction cycles, number of layers, and stacking sequence on compaction force was examined. In contrast to other studies, the area of interest is limited to 40–50% fiber volume content (FVC), which is based on current continuous preforming conditions. The results showed that higher testing speeds result in increased compaction forces. Pre-compaction cycles (up to 8) significantly reduce (up to 69%) the required compaction forces of preforms for continuous preforming. Furthermore, at an equal total superficial density (1800 g/m2), 6-ply preforms (300 g/m2 each ply) require 75–88% higher compaction forces than 3-ply preforms (600 g/m2 each ply). This relation remains constant with decreasing or increasing total superficial density (ply number). Also the stacking sequence of 6-ply preforms (300 g/m2 each ply) remarkably influences the compaction force, whereby the stitching seam pattern and their alignment (superposition) to each other were the main influencing factors. POLYM. COMPOS., 38:2609–2625, 2017. © 2015 Society of Plastics Engineers