Elastomer composite based on EPDM reinforced with polyaniline coated curauá fibers prepared by mechanical mixing

Curauá fibers were used to reinforce elastomeric matrices with polyaniline (PAni) synthesized directly on the fiber surfaces to produce antistatic‐reinforced composites. In this work, composites of poly(ethylene‐co‐propylene‐co‐diene) with curauá fibers coated with PAni were prepared by mechanical mixing in a counter‐rotating twin rotor internal mixer. Then, mechanical and electrical properties of these composites were correlated to Raman and Fourier transformed infrared spectra (FTIR) using chemometric data analyze, such as principal component analysis (PCA) and hierarchical cluster analysis (HCA). Raman spectra showed correlation with electrical properties of conductive composites while FTIR spectra showed good correlation with mechanical properties. EPDM reinforced with PAni coated curauá fibers presented higher tensile strength and modulus than EPDM reinforced with pristine curauá fibers, indicating that the reinforcement effect was obtained. Chemical interaction between the phases occurs with formation of hydrogen bonding between the aminic nitrogens of PAni and the carbonyl groups of lignin of the fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40056.     

Effect of curauá fiber content on the properties of poly(hydroxybutyrate‐co‐valerate) composites

Poly(hydroxybutyrate‐co‐valerate) (PHBV), a biodegradable polymer produced from a renewable microbiological source, was reinforced with varying amounts of curauá fibers (CFs). The composites were produced using a twin‐screw extrusion and injection process. Scanning electron microscopy showed poor adhesion between the matrix and fiber; however, mechanical testing showed that the addition of the fiber improved the mechanical properties. Composites with 20 and 30 wt% CF displayed the best properties; however, because of the difficulties in processing composites with a CF content of 30 wt%, it was concluded that the ideal content of CF was 20 wt%. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Synthesis of glass fiber‐multiwall carbon nanotube hybrid structures for high‐performance conductive composites

The conductive polyamide 66 (PA66)/carbon nanotube (CNT) composites reinforced with glass fiber‐multiwall CNT (GF‐MWCNT) hybrids were prepared by melt mixing. Electrostactic adsorption was utilized for the deposition of MWCNTs on the surfaces of glass fibers (GFs) to construct hybrid reinforcement with high‐electrical conductivity. The fabricated PA66/CNT composites reinforced with GF‐MWCNT hybrids showed enhanced electrical conductivity and mechanical properties as compared to those of PA66/CNT or PA66/GF/CNT composites. A significant reduction in percolation threshold was found for PA66/GF‐MWCNT/CNT composite (only 0.70 vol%). The morphological investigation demonstrated that MWCNT coating on the surfaces of the GFs improved load transfer between the GFs and the matrix. The presence of MWCNTs in the matrix‐rich interfacial regions enhanced the tensile modulus of the composite by about 10% than that of PA66/GF/CNT composite at the same CNT loading, which shows a promising route to build up high‐performance conductive composites. POLYM. COMPOS. 34:1313–1320, 2013. © 2013 Society of Plastics Engineers     

Natural Brazilian Amazonic (Curauá) Fibers Modified with Polyaniline Nanoparticles

The surface of natural Brazilian amazonic fibers (curauá, Ananas erectifolius) was modified with polyaniline nanoparticles, through in situ preparation of polyaniline nanoparticles in presence of the curauá fibers. This allowed for a significant increase in the electrical conductivity of the fibers (≈2 500 times). As the electrical resistivity of the modified fibers is a function of the applied external pressure, the produced composites can be used as a cheap pressure‐sensing material. The modified materials were also characterized by FT‐IR, XPS and SAXS, and the obtained results were used to explain some of the observed characteristics of the materials.

     

Improvement of mechanical properties of natural fiber–polypropylene composites using successive alkaline treatments

The use of natural fibers (NFs) in polymer composites for structural applications has increased greatly in the last years, owing to their abundance and biodegradability. In this work, an innovative and simple successive alkali treatment has been developed to improve the mechanical properties of NFs/polypropylene (PP) composites. Three different cellulosic fibers (curauá, jute, and flax) were used, with a fixed proportion of 10 wt %. The fibers were immersed several times in a 5 wt % NaOH solution. Thermogravimetric analysis data showed an improvement in thermal properties of the fibers, as well as the increase of the crystallinity degree was measured by X‐ray diffraction. By Fourier transform infrared spectroscopy, disappearance of characteristics peaks of hemicelluloses and lignin was observed. Finally, mechanical behavior of the NF/PP composites was examined, using dynamic mechanical analysis. The results revealed that the curauá/PP mechanical properties were significantly improved, showing the positive effect of the successive alkali treatments. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41710.     

Effects of nanoclay on the properties of cardanol‐modified‐resol‐epoxy‐novolac composite material

A nanocomposite based on nanoclay and resol that was modified with cardanol, a natural alkyl phenol, shows improvement for the glass‐fiber‐reinforced epoxy‐composite system. Dispersion of the nanocomposite was investigated by X‐ray, showing good results obtained by the in situ polymerization method. The mechanical properties of the final composites were improved by doping a 6 wt% of nanoclay in cardanol‐modified‐resol (CMR) into the epoxy matrix. The results show that a 15 wt% of CMR in epoxy is a most suitable ratio. Using polyamide as a curing agent instead of other traditional systems, such as anhydrides or amines for epoxy resin, overcame important limitations, further allowing for improved processability. The overall composite performance was enhanced. Additionally, the thermal stability of the system was investigated by thermal gravimetric analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3238–3242, 2007     

Microstructure and fracture behavior of (co)injection‐molded polyamide 6 composites with short glass/carbon fiber hybrid reinforcement

The mechanical and fracture properties of injection molded short glass fiber)/short carbon fiber reinforced polyamide 6 (PA 6) hybrid composites were studied. The short fiber composites of PA 6 glass fiber, carbon fiber, and the hybrid blend were injection molded using a conventional machine whereas the two types of sandwich skin–core hybrids were coinjection molded. The fiber volume fraction for all formulations was fixed at 0.07. The overall composite density, volume, and weight fraction for each formulation was calculated after composite pyrolysis in a furnace at 600°C under nitrogen atmosphere. The tensile, flexural, and single‐edge notch‐bending tests were performed on all formulations. Microstructural characterizations involved the determination of thermal properties, skin–core thickness, and fiber length distributions. The carbon fiber/PA 6 (CF/PA 6) formulation exhibits the highest values for most tests. The sandwich skin‐core hybrid composites exhibit values lower than the CF/PA 6 and hybrid composite blends for the mechanical and fracture tests. The behaviors of all composite formulations are explained in terms of mechanical and fracture properties and its proportion to the composite strength, fiber orientation, interfacial bonding between fibers and matrix, nucleating ability of carbon fibers, and the effects of the skin and core structures. Failure mechanisms of both the matrix and the composites, assessed by fractographic studies in a scanning electron microscope, are discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 957–967, 2005     

Unsaturated polyester‐toughened epoxy composites: Effect of sisal fiber on thermal and dynamic mechanical properties

In the present study, the mechanical and thermal properties of sisal fiber‐reinforced unsaturated polyester (UP)‐toughened epoxy composites were investigated. The sisal fibers were chemically treated with alkali (NaOH) and silane solutions in order to improve the interfacial interaction between fibers and matrix. The chemical composition of resins and fibers was identified by using Fourier‐transform infrared spectroscopy. The UP‐toughened epoxy blends were obtained by mixing UP (5, 10, and 15 wt%) into the epoxy resin. The fiber‐reinforced composites were prepared by incorporating sisal fibers (10, 20, and 30 wt%) within the optimized UP‐toughened epoxy blend. Scanning electron microscopy was used to analyze the morphological changes of the fibers and the adhesion between the fibers and the UP‐toughened epoxy system. The results showed that the tensile and flexural strength of (alkali‐silane)‐treated fiber (30 wt%) ‐reinforced composites increased by 83% and 55%, respectively, as compared with that of UP‐toughened epoxy blend. Moreover, thermogravimetric analysis revealed that the (alkali‐silane)‐treated fiber and its composite exhibited higher thermal stability than the untreated and alkali‐treated fiber systems. An increase in storage modulus and glass transition temperature was observed for the UP‐toughened epoxy matrix on reinforcement with treated fibers. The water uptake behavior of both alkali and alkali‐silane‐treated fiber‐reinforced composites is found to be less as compared with the untreated fiber‐reinforced composite. J. VINYL ADDIT. TECHNOL., 23:188–199, 2017. © 2015 Society of Plastics Engineers     

Composites of Plasticized Polyamide 66 and Chemically Modified Vegetal Fibers

This work aims to prepare composites of polyamide 66 with vegetal fibers from curauá, jute, and flax. Alkaline treatment was conducted followed by silanization, improving the thermal properties of treated natural fibers. To reduce the processing temperature of polyamide 66, a combination of LiCl and N-butylbenzenesulfonamide was added to pure polyamide 66. It is shown that plasticizing polyamide 66 is one way to prepare composites with natural fibers using this high temperature polymer. The increase in elastic modulus of polyamide 66 and the decrease in strain at break were observed.     

Effects of methyl methacrylate grafting and polyamide coating on the interfacial behavior and mechanical properties of jute‐fiber‐reinforced polypropylene composites

In recent years, environmentally friendly materials have become popular because of the growing environmental demands in human society. Natural fibers are now widely used as reinforcements in polymer matrix composites for their various advantages such as low cost, light weight, abundant resources, and biodegradability. However, the applications of these kinds of composites are limited because of their unsatisfactory mechanical properties, which are caused by the poor interfacial compatibility between the fibers and the thermoplastic matrix. In this paper, three methods, including (i) alkali treatment, (ii) alkali and methyl methacrylate (MMA) treatment, and (iii) alkali and polyamide (PA) treatment (APT), were used to treat jute fibers and improve the interfacial adhesion of jute‐fiber‐reinforced polypropylene (PP) composites (JPCs). The mechanical properties of the JPCs were tested, and their impact fracture surfaces were observed. Infrared spectral analysis showed that MMA was grafted and that PA was coated onto the surface of jute fibers. Mechanical tests indicated that the three kinds of pretreated composites presented better mechanical properties than untreated composites. Among them, the APT composite had the best comprehensive properties. Compared with untreated composites, the tensile strength, flexural strength, and flexural modulus of APT composite were increased by 24.8, 31.3, and 28.4%, respectively. Analysis by scanning electron microscopy showed that better interfacial compatibility between jute fibers and PP occured in this kind of composite. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Electrically conductive composites based on epoxy resin containing polyaniline–DBSA‐ and polyaniline–DBSA‐coated glass fibers

Four kinds of polyaniline (PANI)‐coated glass fibers (GF–PANI) combined with bulk PANI particles were synthesized. GF–PANI fillers containing different PANI contents were incorporated into an epoxy–anhydride system. The best conductivity behavior of the epoxy/GF–PANI composites was obtained with a GF–PANI filler containing 80% PANI. Such a composite shows the lowest percolation threshold at about 20% GF–PANI or 16% PANI (glass fiber‐free basis). The PANI‐coated glass fibers act as conductive bridges, interconnecting PANI particles in the epoxy matrix, thus contributing to the improvement of the conductivity of the composite and the lower percolation threshold, compared with that of a epoxy/PANI–powder composite. Particularly, the presence of glass fibers significantly improves the mechanical properties, for example, the modulus and strength of the conductive epoxy composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1329–1334, 2004     

Preparation and characterization of poly[(butylene succinate)‐co‐(butylene adipate)]/carbon nanotube‐coated silk fiber composites

Biodegradable composites consisting of aliphatic polyesters (poly[(butylenes succinate)‐co‐(butylenes adipate)] (PBSA)) and Bombyx mori silk fibers coated with carbon nanotubes (CNTs) were prepared by melt compression molding. The mechanical properties of PBSA were enhanced by the incorporation of a small amount (3 wt%) of CNT‐coated silk fibers, while allowing its potential biodegradability to be retained, which could make these composites good candidates for commodity materials such as general‐purpose plastics. This improvement is attributed to the interactions between PBSA and CNT‐coated silk fibers in the composites. The average interfacial shear strength of the composites consisting of CNT‐coated silk fibers and PBSA matrix was 1.7 MPa, as measured by the microbond droplet test, while that of composites consisting of pure silk fibers and PBSA was only 1.1 MPa. The morphology of the CNT‐coated silk fiber‐reinforced composites was observed using scanning electron microscopy. Copyright © 2007 Society of Chemical Industry     

Effect of nanoclay on physical,mechanical, and microbial degradation of jute‐reinforced,soy milk‐based nano‐biocomposites

Jute‐reinforced, soy milk‐based nano‐biocomposites were fabricated using both natural and organically modified nanoclay to study their effect on physical, mechanical, and degradation properties. Different weight percentages of nanoclays were used to modify soy milk by solution casting process. The jute fibers were then impregnated in modified soy resin and compressed to fabricate nano‐biocomposites. About 5 wt% of organically modified nanoclay‐loaded jute composite showed maximum tensile and flexural strength. X‐ray diffraction and transmission electron microscopy (TEM) analysis of fabricated composites confirmed about the formation of nanostructure. Impact, microhardness, dynamic mechanical analysis results of nano‐biocomposites revealed that nanoclay has influenced to improve such physical and mechanical properties. Microbial degradation study of nano‐biocomposites was carried out in cultured fungal bed. Weight loss, tensile loss, and field emission scanning electron microscopy photographs of composites revealed that composites are biodegradable in nature. The prime advantages of these composite are their eco‐compatibility as jute and soy resin, the basic constituents of composites are biodegradable in nature. These composites can be utilized in automobile, packaging, furniture sectors by replacing nondegradable plastic‐based composite. POLYM. ENG. SCI., 54:345–354, 2014. © 2013 Society of Plastics Engineers     

Polyamide‐6 composites reinforced with cellulose fibers and fabricated by extrusion: Effect of fiber bleaching on mechanical properties and stability

We prepared polyamide‐6 (PA‐6) composites using bleached and semibleached cellulose fibers from Eucalyptus species by processing in a corotating interpenetrating twin‐screw extruder. PA‐6 is a challenging matrix because of its high processing temperature, which overlaps the thermodegradation temperature of the fibers. The selection of the processing conditions for extrusion and the use of the lubricant ethylene bis (stearamide) permitted the production of composites with 20, 30, and 40 wt% of bleached fibers, which are lighter than the corresponding glass fiber composites. Composites with 30 wt% of bleached fibers yield the best mechanical properties and good fiber/matrix interaction, as demonstrated by mechanical tests and scanning electron microscopy. X‐ray photoelectron spectroscopy studies showed that the natural moisture in the fibers promotes the fiber/matrix interaction through the formation of ester bonds. We assessed the effect caused by the presence of lignin in the fibers. Composites containing 30 wt% of semibleached fibers maintained the flexural properties and showed small improvements in thermal stability when compared with bleached fiber composites; however, there is a slight decrease in the tensile properties. Through accelerated aging tests, we observed that increased lignin concentration in the fibers reduced the formation of carbonyl compounds on sample surfaces, indicating a stabilization effect. POLYM. COMPOS., 38:299–308, 2017. © 2015 Society of Plastics Engineers     

Thermal degradation and combustion behaviors of flame retarded glass fiber reinforced polyamide 6 composites based on cerium hypophosphite

In this work, cerium hypophosphite (CeHP) was synthesized and characterized by scanning electron microscope (SEM) and thermogravimetric analysis (TGA) test. CeHP presented rod‐like morphological feature with good thermal stability. Subsequently, CeHP was added into glass fiber reinforced polyamide 6 (GFPA) to develop flame retardant glass fiber reinforced polyamide 6 composites (FR‐GFPA). The flame retardancy of FR‐GFPA composites was characterized by limiting oxygen index (LOI), Underwriters Laboratories 94 testing (UL‐94), microscale combustion calorimeter, and cone calorimeter test. FR‐GFPA composite with 20 wt% CeHP loading passed UL‐94 V0 rating with a high LOI of 26.5 vol%. Cone Calorimeter test showed that peak of heat release rate (PHRR) and total heat release (THR) of FR‐GFPA composites were reduced 27.1% and 21.1% compared with those of GFPA. The mechanical measurement revealed that the tensile strength first increased and then decreased with the increase of CeHP loading. With 15 wt% CeHP loading, the tensile strength of FR‐GFPA composite was 43.0% higher than GFPA. TGA and char residue characterization revealed that the addition of CeHP could significantly promote the formation of condensed char residue. The FR‐GFPA composites obtained herein exhibited superior combined properties of fire resistance, thermal stability, and mechanical properties, demonstrating that CeHP will be a promising candidate for preparing high performance polyamide composites. POLYM. COMPOS., 37:3073–3082, 2016. © 2015 Society of Plastics Engineers     

PE⁃g⁃MAH对聚酰胺6/导电炭黑复合材料性能的影响

采用马来酸酐接枝聚乙烯（PE-g-MAH）以同时提高聚酰胺6/导电炭黑（PA6/CB）复合材料的抗静电性能和韧性,利用双螺杆挤出机和注射成型机制备了系列PA6/CB、PA6/PE-g-MAH和PA6/PE-g-MAH/CB复合材料,并通过扫描电子显微镜（SEM）、差示扫描量热仪 （DSC） 等观察和表征了材料的形貌和结晶性能,测试了材料的力学性能和抗静电性能。结果表明,添加7.5 %（质量分数,下同）的CB后PA6韧性显著降低,CB对PA6结晶有异相形核作用;PE-g-MAH与PA6有较好的相容性,PE-g-MAH韧相能均匀分散在PA6和PA6/7.5 %CB中;添加PE-g-MAH后可提高CB在PA6中的分散性,改变CB的选择性分布,提高PA6/PE-g-MAH/7.5 %CB三元复合材料的电导性能;添加PE-g-MAH还可显著提高PA6和PA6/CB7.5 %的冲击强度和断裂伸长率;添加少量PE-g-MAH能促进复合材料中PA6的结晶。     

Wood‐fiber‐reinforced poly(lactic acid) composites: Evaluation of the physicomechanical and morphological properties

This article presents the results of a study of the processing and physicomechanical properties of environmentally friendly wood‐fiber‐reinforced poly(lactic acid) composites that were produced with a microcompounding molding system. Wood‐fiber‐reinforced polypropylene composites were also processed under similar conditions and were compared to wood‐fiber‐reinforced poly(lactic acid) composites. The mechanical, thermomechanical, and morphological properties of these composites were studied. In terms of the mechanical properties, the wood‐fiber‐reinforced poly(lactic acid) composites were comparable to conventional polypropylene‐based thermoplastic composites. The mechanical properties of the wood‐fiber‐reinforced poly(lactic acid) composites were significantly higher than those of the virgin resin. The flexural modulus (8.9 GPa) of the wood‐fiber‐reinforced poly(lactic acid) composite (30 wt % fiber) was comparable to that of traditional (i.e., wood‐fiber‐reinforced polypropylene) composites (3.4 GPa). The incorporation of the wood fibers into poly(lactic acid) resulted in a considerable increase in the storage modulus (stiffness) of the resin. The addition of the maleated polypropylene coupling agent improved the mechanical properties of the composites. Microstructure studies using scanning electron microscopy indicated significant interfacial bonding between the matrix and the wood fibers. The specific performance evidenced by the wood‐fiber‐reinforced poly(lactic acid) composites may hint at potential applications in, for example, the automotive and packaging industries. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4856–4869, 2006     

Comparison of the role of milled glass and carbon fibers on mechanical properties of (bisphenol A)‐based epoxy composites

The main target of the current work was to study the mechanical properties of milled E‐glass, S‐glass, and high‐strength (carbon fiber)‐reinforced epoxy composites. At first, tensile behavior of the as‐received fibers was evaluated by conducting different tensile tests. Afterwards, the effects of employing an integral blended coupling agent on the performance of the pure epoxy were investigated by microhardness tests and optical microscopic images. Then, the epoxy composites were prepared simply by mixing and stirring 1, 3, and 5 wt% of the milled fibers with the epoxy resin and its hardener. The effects of mixture degassing and addition of the coupling agent to the mixture were examined based on the mechanical properties of the fabricated composites. Also, scanning electron microscope macro‐ and micrographs of the transverse and longitudinal fracture surfaces were used to study the fracture behavior and identify the active toughening mechanisms. The best results were obtained for the degassed and modified milled (carbon fiber epoxy)‐reinforced composite, which enhanced the tensile strength, elongation, Young's modulus, and toughness up to 12%, 17%, 19%, and 27%, respectively. The current study shows that the composite not only is cost effective but also offers better mechanical properties. J. VINYL ADDIT. TECHNOL., 24:130–138, 2018. © 2016 Society of Plastics Engineers     

Carbon‐Polymer Composite Bipolar Plate for HT‐PEMFC

Graphene reinforced carbon‐polymer composite bipolar plate is developed using resole phenol formaldehyde resin, and conductive reinforcements (natural graphite, carbon black, and carbon fiber) using compression molding technique. Graphene is reinforced into the composite to alter various properties of the composite bipolar plate. The developed composite bipolar plate is characterized and the effect of temperature on mechanical and electrical properties is investigated with an overall aim to achieve benchmark given by US‐DOE and Plug Power Inc. The flexural strength and electrical conductivity of the composites was almost stable with the increase in temperature upto 175 °C. The composite bipolar plate maintained high in‐plane and through‐plane electrical conductivities, which is about 409.23 and 98 S cm^–1, respectively, at 175 °C. The flexural strength and shore hardness of the developed composite was around 56.42 MPa and 60, respectively, at 175 °C, and on further increase in the temperature the mechanical strengths deceases sharply. The electrical and mechanical properties of the composite bipolar plates are within the US‐DoE target. However, the various properties of the composite bipolar plate could not be sustained above 175 °C.     

Epoxy‐modified cyanate ester resin and its high‐modulus carbon‐fiber composites

Epoxy E51‐modified bisphenol A dicyanate (BADCy) and its high‐modulus carbon fiber (M40) reinforced composites were prepared in this research. The carbon‐fiber composites were prepared by autoclave molding. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy of BADCy‐E51 blend systems showed that polycyclotrimerization of BADCy primarily took place at low temperature. Epoxy group reacted with triazine ring group and produced oxazolidinone at high temperature. The data of mechanical properties, water absorption, and heat deflection temperature (HDT) of cured castings showed that the matrix system containing 95 wt% BADCy and 5 wt% E51 had optimum characteristics. Scanning electron microscopy (SEM) analysis of M40 fiber and the fracture surfaces of M40/BADCy‐E51 composite displayed that the adhesion between M40 fiber and BADCy was good though the surface of M40 was inert. The high retention of mechanical properties of M40/BADCy‐E51 composite after long‐term exposure to environmental conditions indicated that the M40/BADCy composite was suitable for space applications. POLYM. COMPOS., 27:402–409, 2006. © 2006 Society of Plastics Engineers