On the development of natural fiber composites of high‐temperature thermoplastic polymers

A new method is presented for the development of natural fiber composites of high‐performance thermoplastic polymers considering poly(phenylene ether) (PPE) and wood flour as an example system. The large gap between the high processing temperature of PPE, typically between 280 and 320°C, and the low decomposition temperature of wood flour, about 200°C, was reduced by using a reactive solvent, a low molecular weight epoxy. The epoxy formed miscible blends with PPE, which offered much lower viscosity compared to PPE and processing temperatures well below the decomposition temperature of wood flour. In addition, the epoxy component accumulated around the polar wood flour particles upon polymerization during the fabrication step. The composite materials consisted of a thermoplastic continuous phase and two dispersed phases, one of polymerized epoxy and the other of wood flour particles coated with polymerized epoxy. These composites offered a significant reduction in density and better mechanical and physical properties when compared to commercially available grades of engineering polymer blends filled with short glass fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2159–2167, 2002     

Surface of cellulosic materials modified with functionalized polyethylene coupling agents

The interfacial adhesion between a wood fiber and a plastic matrix strongly influences the performance of wood‐fiber‐reinforced thermoplastic composites. Fiber surface modification with coupling agents is generally needed to induce bond formation between the fiber and polymer matrix. This study investigated the chemical reactions between cellulosic materials and functionalized polyethylene coupling agents. Both wood flour and cotton cellulose powder were treated with acrylic acid‐functionalized polyethylene and maleic anhydride‐functionalized polyethylene (maleated polyethylene) for surface modifications, and chemical changes resulting from these treatments were followed by a study of the Fourier transform infrared and X‐ray photoelectron spectroscopy spectra. Variations in the band intensities, oxygen‐to‐carbon ratios, and concentrations of unoxidized carbon atoms were related to changes that occurred on the surfaces of modified cellulosic materials. The experimental results indicated that chemical bonds between the hydroxyl groups of the cellulosic materials and the functional groups of the coupling agents occurred through esterification reactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 278–286, 2003     

Incorporation of epoxidized soybean oil as co‐matrix in epoxy resin toward developing plastisol/particulate toughened glass fiber composites

Epoxidized soybean oil was incorporated as a co‐matrix into an epoxy resin, and the hybrid resin system was used for preparing glass fiber‐reinforced composites. Effect of addition of poly(vinyl chloride) plastisol and selected particulate fillers (fly ash and wood flour) to epoxy/epoxidized soybean oil matrix on mechanical and water uptake properties of glass fiber‐reinforced composites were studied. Fourier transform infrared spectroscopy was used to reveal the curing state of these composites. It was observed that tensile strengths and moduli decreased with the inclusion of all additives. However, addition of poly(vinyl chloride) plastisol, fly ash, and wood flour particulate fillers showed significant increase in impact strengths compared with neat epoxy composite in a synergistic manner. Water uptake results of the composites were found to be in good agreement with ? OH peak intensities obtained from Fourier transform infrared spectroscopy. Finally, acousto‐ultrasonic nondestructive technique was successfully used to assess damage states and to relate stress wave factors with tensile strength properties of modified epoxy‐based glass fiber composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40586.     

The rheology and extrusion processing performance of wood/melamine composites

A modified melamine resin that exhibits both thermoplastic and thermoset behaviors was used as a matrix for wood plastic composites (WPCs). The thermoplastic melamine (TPM) resin exhibits a glass transition at approximately 34°C and continues to be thermally malleable until a crosslinking reaction develops with additional heating and an acid catalyst. Varying blends of TPM and wood flour were evaluated for their rheology and curing behavior using torque rheometry. WPC composites were manufactured with extrusion methods and final product properties determined. The torque rheometry results showed a highly dependent relationship of the curing behavior to the amount of wood flour utilized and temperature. Based upon the torque rheometry results, two extrusion platforms were developed to initiate the curing process; (1) cure within the die land and (2) post‐cure of the extrudate. The post‐cure procedure provided composites with higher mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39858.     

Rice‐husk‐ash‐based silica as a filler for embedding composites in electronic devices

We carried out a feasibility study of the use of black rice husk ash (RHA) as a filler in epoxy resin for embedding material in electrical and electronic applications. We made a comparison by mixing RHA and two commercial fillers, fused and crystalline silica, with epoxy resin at weight fractions ranging from 20–60%. RHA‐filled epoxy resin had higher mixing viscosity, coefficient of thermal expansion, and water absorption percentage than commercial‐silica‐filled epoxy composite. However, the impact strength of all composites was comparable, but the tensile strength and elongation at break of silica‐filled epoxy were slightly superior. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3013–3020, 2002     

Heterocyclic‐based epoxy‐terminated structural adhesive. II. Curing,adhesive strength,and thermal stability

We studied the curing behavior of heterocyclic‐based epoxy‐terminated resins using diaminodiphenyl ether, diaminodiphenyl sulfone, benzophenone tetracarboxylicdianhydride, and the commercial hardener of Ciba‐Geigy's two‐pack Araldite as curing agents. The adhesive strength of the adhesives was measured by various ASTM methods such as lap‐shear, peel, and cohesive tests on metal–metal, wood–wood, and wood–metal interfaces. All of these results were compared with those of an epoxy resin prepared from bisphenol‐A and epichlorohydrin resin with an epoxy equivalent value of 0.519. The thermal stability of both the virgin resin and its cured form was also studied by thermogravimetric analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3520–3526, 2002     

Preparation,characterization, and improvement of hollow epoxy particle‐toughened vinyl ester composites for high‐end applications

Spherical hollow epoxy particles (HEPs) that can serve as advanced reinforcing fillers for vinyl ester thermosets were prepared using the water‐based emulsion method. The HEP fillers were incorporated into the vinyl ester matrices at different loading amounts, ranging from 0 to 9 wt %, to reinforce and toughen the vinyl ester composite. The optimum mechanical properties of the HEP‐toughened epoxy composite can be achieved by the addition of 5 wt % HEP filler into the vinyl ester matrices. The toughening and strengthening of the epoxy composites involved the interlocking of vinyl ester resins into the pore regions on the HEP fillers. The toughening and interlocking mechanisms of HEP‐toughened vinyl ester composites were also proposed and discussed. The addition of HEP fillers into vinyl ester matrices increased the glass transition temperature (T_g) and thermal stability of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of chemical treatment of wood flour on the properties of styrene butadiene rubber/polystyrene composites

Composites from SBR/PS blend and the chemically treated wood flour have been prepared. The materials used for such treatment are NaOH, MAN, MAN‐glycidyl methacrylate, and silane coupling agent, used to improve the dispersion of wood flour in the SBR/PS blend. The effects of chemical treatment on curing characteristics, and physicomechanical and electrical properties of SBR/PS composites were studied. The rheological as well as the mechanical parameters were improved by using the modified wood flour with MAN‐glycidyl methacrylate (SMG), followed by SM obtained at 15 phr, while the other treatments slightly affect these parameters. The permittivity ?′ and dielectric loss ?″ were measured in the frequency range from 100 Hz up to 100 kHz and at temperatures ranging from 30 up to 90°C. The dielectric investigations indicate that the samples containing wood flour treated with both SMG and SM increase the values of ?′ and decrease those of ?″, which allow such samples to be used in insulation purposes. The increase in the relaxation time and the crosslinking density ν for such composites indicate the increase in filler–polymer interaction rather than filler–filler interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5861–5870, 2006     

Biodegradability and mechanical properties of agro‐flour–filled polybutylene succinate biocomposites

The objective of this study was the production of rice husk flour (RHF) and wood flour (WF) filled polybutylene succinate (PBS) biocomposites as alternatives to cellulosic material filled conventional plastic (polyolefins) composites. PBS is one of the biodegradable polymers, made from the condensation reaction of 1,4‐butanediol and succinic acid that can be naturally degraded in the natural environment. We compared the mechanical properties between conventional plastics and agro‐flour–filled PBS biocomposites. We evaluated the biodegradability and mechanical properties of agro‐flour–filled PBS biocomposites according to the content and filler particle size of agro‐flour. As the agro‐flour loading was increased, the tensile and impact strength of the biocomposites decreased. As the filler particle size decreased, the tensile strength of the biocomposites increased but the impact strength decreased. The addition of agro‐flour to PBS produced a more rapid decrease in the tensile strength, notched Izod impact strength, and percentage weight loss of the biocomposites during the natural soil burial test. These results support the application of biocomposites as environmentally friendly materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1513–1521, 2005     

Some studies on mechanical properties of wood flour/continuous glass mat/polypropylene composite

The mechanical properties and the surface property of wood flour/continuous glass mat/polypropylene composites have been investigated. The suitability of wood flour as a filler for continuous glass mat–reinforced polypropylene has been tested using different mesh sizes (e.g., 20 and 40 mesh), as well as by varying the weight percentage of wood flour from 0%– 30%. Moreover, different treatments such as coupling agent A‐1100 and functionalized polypropylene grafting with maleic anhydride, and so forth, have also been used to improve the compatibility of wood flour and glass fiber with the polymer resin. In addition, the effects of the surface weight of glass mat and matrix resin have been studied. The extent of the improvement in mechanical properties depends on the wood flour content and size, the surface weight of the glass mat, the matrix resin, and the surface treatment of wood flour. After adding wood flour, the contact angle of distilled water on the composite surface decreases and the polar component of surface tension increases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 536–544, 2002     

Fracture toughness of silica particulate‐filled epoxy composite

The relationship between the postcuring conditions and fracture toughness on three silica particulate‐filled epoxy composites was investigated. The glass transition temperature, T_g, and the fragility parameter, m, derived from the thermo‐viscoelasticity, were used to characterize the composites, which were postcured under various conditions. The glass transition temperature and fragility both depended on both of the curing conditions and the volume fraction of silica particles. The glass transition temperature increased with the postcuring time and temperature, while the fragility generally decreased as the volume fraction increased. There was no direct correlation between the glass transition temperature and fragility. The fracture toughness depended on both the glass transition temperature and fragility. The composites with a high glass transition temperature and low fragility had high fracture toughness. These results indicate that the glass transition temperature and fragility are useful parameters for estimating the fracture toughness of the silica particulate‐filled epoxy composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2261–2265, 2002     

Effect of the processing techniques on the properties of ecocomposites based on vegetable oil‐derived Mater‐Bi® and wood flour

Polymer composites based on biodegradable polymers and natural‐organic fillers are becoming more and more important because of their interesting properties in terms of environmental impact, manufacturing cost, and esthetic features. In particular, the use of biodegradable polymer matrices allows obtaining a full biodegradability. One of the most interesting biodegradable polymer families is the Mater‐Bi® one. In this work, we investigated the processability, the influence of different processing techniques, and the influence of the filler particle size on the properties of Mater‐Bi/wood flour composites. Injection molding caused a partial degradation of the macromolecular chains, whereas single‐screw extrusion followed by calendering and twin‐screw extrusion provoked an increase of the elastic modulus and of the viscosity. The use of wood flour led to a significant increase of the rigidity, whereas a reduction of the ductility was observed. Because of the very similar aspect ratios of the two different filler size classes, no dramatic differences in the properties were found. These results are useful in order predicting and setting up the optimum preparation and processing strategy for the production of fully biodegradable polymer composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of compatibilizers on water absorption kinetics of polypropylene/wood flour foamed composites

Polypropylene (PP)/wood flour foamed composites were prepared by taking PP:wood flour in the ratios of 100 : 0, 90 : 10, 80 : 20, 70 : 30, and 60 : 40 (w/w), with and without compatibilizers like maleic anhydride‐treated wood flour and maleic anhydride‐grafted PP (PPgMA). The foamed composite samples were employed for water swelling at 27°C, 70°C, and in steam. The absorption of water increased with increase in filler contents for all three‐temperature conditions. The maleic anhydride‐treated wood flour and PPgMA showed reduction in water swelling, and the best one was in case of the PPgMA‐foamed composites for respective conditions. Diffusion, sorption, and permeation coefficients were determined to study the absorption kinetics. FTIR spectra were also recorded for 30 wt % of filler loading for all the composites, which showed the effect of compatibilizers on reduction in water absorption in foamed PP/wood flour composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2530–2537, 2006     

Evaluation of dynamic elastic properties of wood‐filled polypropylene composites

Dynamic modulus of elasticity (MoE) and shear modulus of wood‐filled polypropylene composite at various filler contents ranging from 10% to 50% was determined from the vibration frequencies of disc‐shaped specimens. Wood filler was used in both fiber form (pulp) and powder form (wood flour). A novel compatibilizer, m‐isopropenyl‐α,α‐dimethylbenzyl‐isocyanate(m‐TMI) grafted polypropylene with isocyanate functional group was used to prepare the composites. A linear increase in dynamic MoE, shear modulus, and density of the composite was observed with the increasing filler content. Between the two fillers, wood fiber filled composites exhibited slightly better properties. At 50% filler loading, dynamic MoE of the wood fiber filled composite was 97% higher than that of unfilled polypropylene. Halpin‐Tsai model equation was used to describe the changes in the composite modulus with the increasing filler content. The continuous improvement in elastic properties of the composites with the increasing wood filler is attributed to the effective reinforcement of low‐modulus polypropylene matrix with the high‐modulus wood filler. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1706–1711, 2006     

Soybean and linseed oil‐based composites reinforced with wood flour and wood fibers

Composites consisting of a conjugated linseed or soybean oil‐based thermoset reinforced with wood flour and wood fibers have been prepared by free radical polymerization. The thermoset resin consists of a copolymer of conjugated linseed oil (CLO) or conjugated soybean oil (CSO), n‐butyl methacrylate (BMA), divinylbenzene (DVB), and maleic anhydride (MA). The composites were cured at 180°C and 600 psi and postcured for 2 h at 200°C under atmospheric pressure. The effect of varying filler load, time of cure, filler particle size, origin of the fillers, and resin composition has been assessed by means of tensile tests, DMA, TGA, Soxhlet extraction followed by ¹H‐NMR spectroscopic analysis of the extracts, and DSC. The best processing conditions have been established for the pine wood flour composites. It has been observed that the addition of MA to the resin composition improves the filler‐resin interaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical characterization of polypropylene–wood flour composites

The mechanical performance of different wood flour/polypropylene (PP) composites with interface modifications was compared. Wood flour was incorporated into the matrix after esterification with maleic anhydride (MAN) or without any modification but with the addition of a compatibilizing agent [maleic anhydride–polypropylene copolymer (PPMAN)] to modify the polymer–filler interaction. Composites were prepared by injection molding with different concentrations of wood flour. Mechanical properties (except Young's modulus) were not improved either by the wood flour chemical modification or by the use of PPMAN. However, both compatibilization methods were successful in improving the dispersion of the wood flour in the PP matrix. Creep behavior of composite samples was improved by the addition of PPMAN, whereas the composites prepared from MAN‐treated wood flour showed larger deformations than composites made with untreated particles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1420–1428, 2003     

Cure characteristics,mechanical properties,and morphological studies of linoleum flour‐filled NBR compounds

The effects of the content and size of the filler on the curing characteristics and mechanical properties of linoleum flour‐reinforced acrylonitrile‐butadiene rubber (NBR) composites are analyzed. The linoleum flour was obtained from wastes of linoleum production. The effects of this filler are compared with those of two other kinds of lignocellulosic fillers. Four filler percentages (10, 20, 30 and 40 phr) were added to the rubber. The morphology of the fillers was studied and then related to the curing and mechanical characteristics of the studied compounds. The results indicate that all the fillers behave as vulcanizing agents, accelerating the vulcanization process, which is reflected in a significant decrease of the optimum cure time. In this case, linoleum is the most effective one; however, it produces lower mechanical properties than the other two systems. The results obtained together with the positive environmental impact in the recycling of production wastes would justify the use of linoleum flour in rubber technology. Polym. Eng. Sci. 44:909–916, 2004. © 2004 Society of Plastics Engineers.     

Kenaf‐filled biodegradable composites: rheological and mechanical behaviour

Biodegradable polymer composites, typically based on biodegradable polymer matrices and natural‐organic fillers, are gaining rising interest and importance over the last few years. Several natural‐organic fillers can be used but the most widespread so far is wood, in the form of fibres or flour. Alternative cellulosic fillers can ensure advantages in terms of resource utilization and properties of the final composite. In this work, Mater‐Bi^® based biodegradable composites were prepared with two kinds of wood flour, and directly compared with alternative composites containing kenaf fibres. The use of kenaf fibres allowed improved elastic modulus, tensile strength and interaction with the polymer matrix to be obtained, although the filler dispersion was worse. Rheological measurements evidenced higher viscosity and an increasingly elastic behaviour of the melt. Copyright © 2012 Society of Chemical Industry     

The conductivity behavior of multi‐component epoxy,metal particle,carbon black,carbon fibril composites

Following the previous studies of epoxy/silver conductive composites, a detailed investigation of the influence of ethylene glycol on the resulting resistivity of various composites was carried out. Ethylene glycol was found to have a catalytic effect on the curing process of the epoxy resin, verified by differential scanning calorimetry studies. The accelerated curing process diminishes settling of the metal particles and therefore results in better and more uniform conductivities. High temperature curing of the composites was found to have a similar effect on the conductivity. The conductivity behavior of some other composites, such as epoxy/nickel, epoxy/nickel/carbon fibrils, and epoxy/carbon black/carbon fibrils, were also studied. The structure–property relations were better understood through scanning electron microscopy observations. Silver and nickel particles were found to perform differently in the cured epoxy, showing different percolation concentrations and conductivity levels. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1706–1713, 2002     

Influence of the zeolite type on the mechanical–thermal properties and volatile organic compound emissions of natural‐flour‐filled polypropylene hybrid composites

The physicomechanical properties, thermal properties, odor, and volatile organic compound (VOC) emissions of natural‐flour‐filled polypropylene (PP) composites were investigated as a function of the zeolite type and content. The surface area and pore structure of the natural and synthetic zeolites were determined by surface area analysis and scanning electron microscopy, respectively. With increasing natural and synthetic zeolite content, the tensile and flexural strengths of the hybrid composites were not significantly changed, whereas the water absorption was slightly increased. The thermal stability and degradation temperature of the hybrid composites were slightly increased with increasing natural and synthetic zeolite content. At natural and synthetic zeolite contents of 3%, the various odors and VOC emissions of the polypropylene/rice husk flour and polypropylene/wood flour hybrid composites were significantly reduced because of the absorption of the odor and VOC materials in the pore structures of the natural and synthetic zeolites. These results suggest that the addition of natural and synthetic zeolites to natural‐flour‐filled thermoplastic polymer composites is an effective method of reducing their odor and VOC emissions without any degradation of their mechanical and thermal properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008