Preparation and characterization of electroconductive polypyrrole–thermoplastic composites

Polypyrrole–thermoplastic composite films were obtained by casting. Homogeneous films were prepared with dispersant poly(vinyl methyl ether) or poly(vinyl ethyl ether) by two methods. Electric conductivity, morphology, mechanical properties, and sensitivity to H₂O₂ in water were studied. Composites of polypyrrole with poly(vinyl chloride) carboxylated and poly(vinyl methyl ether) presented improved mechanical and electrical properties compared with other composites studied. These films were sensitive to H₂O₂ in water, showing a significant change in electric resistance. This change is discussed in relation to the H₂O₂ concentration and the exposure time. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1498–1506, 2001     

Microwave properties of selected thermoplastic conducting composites

Thermoplastic conducting composites of polyparaphenylene diazomethine (PPDA), polythiophene (PTH), poly‐3,4‐Ethylenedioxythiophene (PEDOT), and polyaniline (PANI) with polyvinylchloride (PVC) and polyurethane (PU) were prepared. Conducting composites were prepared by in situ polymerization of thiophene, ethylene dioxy thiophene, and aniline in the presence of polyvinyl chloride and polyurethane using FeCl₃ as the oxidizing agent. PPDA composites were prepared by dispersing PPDA powder in the polymer solution followed by casting. The microwave properties of all the composites were studied in the S band using Vector Network Analyzer and the best composite was selected based on the dielectric properties for microwave applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A comparison study of lignocellulosic–thermoplastic composites prepared from different compounding techniques

A comparison study was carried out to determine the effect of different types of compounding technique, i.e., internal mixer, twin screw extruder, and high speed mixer in the preparation of kenaf‐polypropylene composite. The effect of percentage kenaf loading and particle size of kenaf (core) on the flexural properties of the composite was investigated. From the results, the incorporation of kenaf, regardless of particle size had resulted in the reduction of flexural strength of the composite. However, flexural modulus of the composites increased as the percentage of kenaf loading was increased due to the increasing of the stiffness contributed by kenaf fiber. Composites produced from internal mixer had displayed higher flexural properties as compared to those prepared from high speed mixer and twin screw extruder. It was believed that this phenomenon was attributed to the effectiveness of internal mixer with a better compounding mechanism which improved the wetting and distribution on kenaf within the polypropylene matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and viscoelastic properties of butadiene–styrene thermoplastic and oxidized carbon fibre composites

The mechanical and dynamic properties of oxidized carbon fibre and butadiene–styrene thermoplastic elastomer (SBS) composites were studied as a function of the level of fibre oxidation and in comparison with the properties of composites reinforced with untreated commercial carbon fibre. As a general rule, fibre oxidation gives rise to materials with improved mechanical properties—greater tensile and tear strengths. The improvements accomplished depend on the degree of fibre oxidation. The effects of long exposure times to oxidizing agents were tested on the experimental samples, i.e. increase in the number of functional surface groups and loss in mechanical strength due to a decrease in the L/d ratio, properties which act in opposite directions in the composite. Storage modulus retention with increasing strain amplitude is directly proportional to the number of functional groups incorporated into the fibre surface, whereas at low strain amplitude it is proportional to fibre strength, measured in terms of the L/d ratio after processing. It is suggested that improved adhesion at the matrix–fibre interface is obtained through the functional groups of the oxidized fibre. As a consequence of fibre–matrix interface and at any frequency, the damping peak temperature is shifted towards higher ranges and at the same time the apparent activation energy of the relaxation process is observed to increase.     

长纤维增强热塑性复合材料的开发与应用

长纤维增强热塑性复合材料以其优异的性能成为高分子复合材料研发与应用的热点。笔者综述了长纤维增强热塑性复合材料的性能特征、研发历史与现状、产品形式与制造技术、应用状况,展望了长纤维增强热塑性复合材料的发展前景。     

Influence of thermoplastic elastomers on adhesion in polyethylene–wood flour composites

The mechanical properties of recycled low-density polyethylene/wood flour (LDPE/WF) composites are improved when a maleated triblock copolymer styrene–ethylene/butylene–styrene (SEBS–MA) is added as a compatibilizer. The composites' tensile strength reached a maximum level with 4 wt % SEBS–MA content. The compatibilizer had a positive effect on the impact strength and elongation at break but decreased the composites' stiffness. Dynamic mechanical thermal analysis (DMTA), a lap shear adhesion test, and a scanning electron microscope (SEM) were used to investigate the nature of the interfacial adhesion between the WF/SEBS and between the WF/SEBS–MA. Tan δ peak temperatures for the various combinations showed interaction between the ethylene/butylene (EB) part of the copolymer and the wood flour in the maleated system. The shear lap test showed that adhesion between the wood and SEBS–MA is better than between the wood and SEBS. The electron microscopy study of the fracture surfaces confirmed good adhesion between the wood particles and the LDPE/SEBS–MA matrix. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1845–1855, 1998     

Elaboration of performance of tea dust–polypropylene composites

In this research work, dynamic, mechanical, and thermophysical properties of untreated and 5, 7, and 10 wt % styrene treated tea dust (TD):polypropylene (PP) composites prepared by injection‐molding machine were elaborated. There were distinctive and significant improvement observed in mechanical properties (tensile strength, tensile modulus, and elongation at break), physical analysis (water swelling), dynamic mechanical properties (storage modulus, loss modulus, and tan δ), and thermal behavior and surface morphological properties of styrene treated TD:PP (40:60) composites as compared to that of untreated one. The tensile strength (from 7.00 to 9.95 MPa), tensile modulus (from 350 to 715 MPa), storage modulus (from 8500 to ～10,500 MPa), and loss modulus (from ～150 to ～200 MPa) increased on 10 wt % styrene treatment of TD over the untreated TD:PP (40:60) composites. The styrene treated TD:PP (40:60) composites behaved as more elastic than their pure counterpart. Styrene treated TD:PP (40:60) composites were more thermally more stable (85 °C difference) as compared to virgin PP. Overall, this research also indicates the use of TD waste. An improvement in dispersion of styrene treated TD particles in PP was also observed in the preparation of the PP composites due to good compatibility of styrene with PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44750.     

连续纤维增强热塑性树脂基复合材料拉挤工艺研究与应用现状

拉挤工艺是一种能够经济的连续生产复合材料的典型制造工艺，它不但具有其它成型方法的优点，而且还具有其它工艺所不具备的优点，如生产效率高，重复性好，长度可任意切断，省原料、省能耗等。本文简要介绍了连续纤维增强热塑性树脂基复合材料拉挤工艺研究与应用的现状，包括目前国内外主要的拉挤工艺，以及拉挤工艺过程的若干工序。     

Influence of starch on the properties of carbon‐black‐filled styrene–butadiene rubber composites

The influence of starch on the properties of carbon‐black‐filled styrene–butadiene rubber (SBR) composites was investigated. When the starch particles were directly melt‐mixed into rubber, the stress at 300% elongation and abrasion resistance decreased evidently with increasing starch amount from 5 to 20 phr. Scanning electron microscopy observations of the abrasion surface showed that some apparent craters of starch particles were left on the surface of the composite, which strongly suggested that the starch particles were large and that interfacial adhesion between the starch and rubber was relatively weak. To improve the dispersion of the starch in the rubber matrix, starch/SBR master batches were prepared by a latex compounding method. Compared with the direct mixing of the starch particles into rubber, the incorporation of starch/SBR master batches improved the abrasion resistance of the starch/carbon black/SBR composites. With starch/SBR master batches, no holes of starch particles were left on the surface; this suggested that the interfacial strength was improved because of the fine dispersion of starch. Dynamic mechanical thermal analysis showed that the loss factor at both 0 and 60°C increased with increasing amount of starch at a small tensile deformation of 0.1%, whereas at a large tensile strain of 5%, the loss factor at 60°C decreased when the starch amount was varied from 5 to 20 phr. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Photodegradation of thermoplastic elastomeric rubber–polyethylene blends

The photodegradation of a new family of thermoplastic elastomers, based on blends of natural rubber and polyethylene, was studied with laboratory ultraviolet exposures in the unstrained state and under tensile strain (25 and 50%). Strained exposure caused reduction of the strain to failure in subsequent tensile tests. The blends were more resistant to degradation than the natural rubber homopolymer. The introduction of crosslinks (at a low concentration so that the thermoplastic nature of the blends was retained) changed the resistance to photo‐oxidation. Two different crosslinking systems were used. When dicumyl peroxide was used as the crosslinking agent, the resistance to degradation was reduced, whereas the compound containing a sulfur curing system showed improved resistance to photodegradation. Photo‐oxidation rather than ozone degradation was found to be the major cause of breakdown, even with samples held in tension. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2393–2402, 2002     

Preparation of soft wood–plastic composites

To extend the applications of wood–plastic composites (WPCs), soft WPCs were prepared with ethylene vinyl acetate (EVA) and wood flour (WF) as major components via a two‐step process involving two‐roll mixing and compression molding. The effect of the various factors, such as WF, unsaturated fatty acid (UFA), and dicumyl peroxide contents, on the mechanical properties, processability, and morphology of the WPCs was investigated in detail. The addition of UFA could effectively improve the processability and flexibility of the composites. The in situ grafting reaction between UFA and EVA considerably improved the adhesion of the WF and resin matrix. Consequently, soft WPCs with good performances in flexibility and processability were successfully obtained. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nonlinear stress relaxation of silica filled solution‐polymerized styrene–butadiene rubber compounds

The stress relaxation of silica (SiO₂) filled solution‐polymerized styrene–butadiene rubber (SSBR) has been investigated at shear strains located in the nonlinear viscoelastic regions. When the characteristic separability times are exceeded, the nonlinear shear relaxation modulus can be factorized into separate strain‐ and time‐dependent functions. Moreover, the shear strain dependence of the damping function becomes strong with an increase in the SiO₂ volume fraction. On the other hand, a strain amplification factor related to nondeformable SiO₂ particles can be applied to account for the local strain of the rubbery matrix. Furthermore, it is believed that the damping function is a function of the localized deformation of the rubbery matrix independent of the SiO₂ content. The fact that the time–strain separability holds for both the unfilled SSBR and the filled compound indicates that the nonlinear relaxation is dominated by the rubbery matrix, and this implies that the presence of the particles can hardly qualitatively modify the dynamics of the polymer. It is thought that the filler–rubber interaction induces a coexistence of the filler network with the entanglement network of the rubbery phase, both being responsible for the nonlinear relaxation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

凯芙拉纤维/尼龙6热塑性复合材料的研制

研究了凯芙拉纤维与尼龙 6单体通过阴离子原位聚合制备热塑性复合材料的方法。以氢氧化钠为引发剂 ,甲苯二异氰酸酯 (TDI)为活化剂 ,确定体系的聚合温度为 160℃ ,引发剂、活化剂用量为6.42 m ol/L ,聚合时间 60 min,在此条件下聚合速度较快 ,单体转化率 1h后达 95 %以上。研究发现 ,凯芙拉纤维经酰化处理后 ,基本上不会对己内酰胺阴离子聚合体系产生阻聚作用     

Thermal and electrical conductivity of carbon–filled liquid crystal polymer composites

The thermal and electrical conductivity of resins can be increased by adding conductive carbon fillers. One emerging market for thermally and electrically conductive resins is for bipolar plates for use in fuel cells. In this study, varying amounts of five different types of carbon, one carbon black, two synthetic graphites, one natural flake graphite, and one calcined needle coke, were added to Vectra A950RX Liquid Crystal Polymer. The resulting composites containing only one type of filler were then tested for thermal and electrical conductivity. The objective of this work was to determine which carbon filler produced a composite with the highest thermal and electrical conductivity. The results showed that composites containing Thermocarb TC‐300 synthetic graphite particles had the highest thermal and electrical conductivity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99; 1552–1558, 2006     

Next generation high‐performance carbon fiber thermoplastic composites based on polyaryletherketones

Interest in carbon fiber reinforced composites based on polyaryl ether ketones (PAEKs) continues to grow, and is driven by their increasing use as metal replacement materials in high temperature, high‐performance applications. Though these materials have seen widespread use in oil, gas, aerospace, medical and transportation industries, applications are currently limited by the thermal and mechanical properties of available PAEK polymer chemistries and their carbon fiber composites as well as interfacial bonding with carbon fiber surfaces. This article reviews the state of the art of PAEK polymer chemistries, mechanical properties of their carbon fiber reinforced composites, and interfacial engineering techniques used to improve the fiber‐matrix interfacial bond strength. We also propose a roadmap to develop the next generation of high‐performance long fiber thermoplastic composites based on PAEKs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44441.     

Natural fiber suspensions in thermoplastic polymers. I. Analysis of fiber damage during processing

The final properties of the composites materials are strongly dependent on the residual aspect ratio, orientation, and distribution of the fibers, which are determined by the processing conditions. Present work is a systematic study of the influence of natural fiber concentration on its damage during all the steps involved in the composite compounding. The system under study is cellulose fiber‐reinforced polypropylene. The fiber geometrical parameters—length, diameter, and aspect ratio—are measured, and their statistical distributions are assessed for different concentrations. It is found that the higher the fiber concentration, the lower the fiber damage. These results evidence a difference in behavior between the damage of flexible natural fiber and rigid ones. The results are analyzed in terms of fiber concentration regimes, fiber–fiber interaction, flexibility, and entanglements. Two competitive mechanisms of the fiber interaction are proposed for explaining the fiber damage behavior during the flow of the flexible natural fiber suspensions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2501–2506, 2007     

连续碳纤维热塑性复合材料制备工艺研究

对近年来的碳纤维热塑性复合材料预浸料制备技术、成型工艺及其在电子电气中的应用现状进行了综合论述．     

Stress relaxation and inverse stress relaxation in silk fibers

Stress‐relaxation experiments on four varieties of Indian silk fiber show that stress relaxation is significantly greater in non‐Mulberry silks than in the Mulberry silk and that the differences among non‐Mulberry silk fibers are relatively small. All the fibers studied also exhibit inverse stress relaxation. It has been shown that the Maxwell–Wiechert model, with two Maxwell elements in parallel, can be used to analyze and explain both the stress‐relaxation and inverse stress‐relaxation behaviors. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1147–1154, 2001     

Processing–formulation–performance relationships of polypropylene/short flax fiber composites

This work is a comprehensive study of the effect of extrusion process parameters and formulation on the properties of polypropylene (PP)/short flax fiber composites. The parameters that were varied during the twin‐screw extrusion process were screw configuration, revolutions per minute (rpm), extrusion temperature, and flow rate. The effect of the feeding zone location of cellulosic fiber was also considered. This study investigates the effect of the formulation, cellulosic fiber content, the presence of a coupling agent, and of a reactive additive on composite performance. The composites were characterized in terms of morphology and microstructure, fiber length, rheological, thermal, and mechanical properties. Sensibility to humidity and recyclability were also considered. When compared with as‐received PP, the tensile strength of injection‐molded parts increased with cellulosic content by up to 40 vol %, and the tensile modulus increased 3.5 times when a combination of coupling and reactive agents was used. Exposed to controlled humidity of 50% during 1 year, these composites exhibited a very low level of humidity uptake around 0.85 wt %. The processability of these materials using a cast film line and the mechanical properties of extruded sheets are also presented. Furthermore, these materials demonstrate a good recyclability using injection molding by keeping the integrality of their mechanical properties after five reprocessing cycles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41528.     

Dielectric properties of aluminum–epoxy composites

Dielectric properties of Al–epoxy composites were characterized as a function of composition, frequency, and temperature. The dielectric constant increased smoothly with an increase in the concentration of aluminum. An increase in dielectric constant was also observed with an increase in temperature as well as with a decrease in frequency. In general, dissipation factor values for composites with higher concentrations of aluminum were greater than those with lower volume content of aluminum. Also, the dissipation factor showed an increase both with a decrease in frequency and an increase in temperature. The increase in values of dielectric constant and dissipation factor with an increase in concentration of aluminum was attributed to interfacial polarization. The absence of any discontinuity in the plot of dielectric constant versus composition was ascribed to the absence of continuous aluminum chains in the composition range investigated. The increase in dielectric constant with a rise in temperature was attributed to the segmental mobility of the polymer molecules. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3602–3608, 2003