Characterization of highly filled wood flour–PVC composites: Morphological and thermal studies

Composites with polyvinyl chloride (PVC) as major matrix constituent, ethylene vinyl acetate (EVA) as polymeric plasticizer and wood flour (WF) and fly ash (FA) as filler were extruded. Morphology of the samples was studied using scanning electron microscopy (SEM). Morphological study indicated good dispersion of the constituents. Infrared spectroscopy (IR) indicates interaction between EVA and PVC and also between the polymeric matrix and WF. The effect of various constituents on glass transition temperature (T_g) was evaluated using differential scanning calorimetry. Addition of EVA decreased the T_g, whereas T_g was increased due to addition of WF and FA. Study indicated that reduction in T_g on addition of EVA was compensated by increase in T_g due to addition of WF. The contribution of FA to change in T_g was not significant. Resulting composites have T_g close to that of PVC. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Flammability and mechanical properties of wood flour‐filled polypropylene composites

Polypropylene (PP) composites filled with wood flour (WF) were prepared with a twin‐screw extruder and an injection‐molding machine. Three types of ecologically friendly flame retardants (FRs) based on ammonium polyphosphate were used to improve the FR properties of the composites. The flame retardancy of the PP/WF composites was characterized with thermogravimetric analysis (TGA), vertical burn testing (UL94‐V), and limiting oxygen index (LOI) measurements. The TGA data showed that all three types of FRs could enhance the thermal stability of the PP/WF/FR systems at high temperatures and effectively increase the char residue formation. The FRs could effectively reduce the flammability of the PP/WF/FR composites by achieving V‐0 UL94‐V classification. The increased LOI also showed that the flammability of the PP/WF/FR composites was reduced with the addition of FRs. The mechanical property study revealed that, with the incorporation of FRs, the tensile strength and flexural strength were decreased, but the tensile and flexural moduli were increased in all cases. The presence of maleic anhydride grafted polypropylene (MAPP) resulted in an improvement of the filler–matrix bonding between the WF/intumescent FR and PP, and this consequently enhanced the overall mechanical properties of the composites. Morphological studies carried out with scanning electron microscopy revealed clear evidence that the adhesion at the interfacial region was enhanced with the addition of MAPP to the PP/WF/FR composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of hydrothermal environment on moisture absorption and mechanical properties of wood flour–filled polypropylene composites

The moisture absorption and mechanical properties of wood flour–filled polypropylene composites in a hydrothermal environment have been studied by immersing the composites in water at 23, 60, and 100°C. The degree of moisture absorption was found to be dependent on the modification of matrix, the weight percentage, mesh size, and surface treatment of wood flours. It increased with increasing the immersion temperature. The tensile strength of all composites with wood flours of different contents, mesh sizes, and surface treatments increased after immersion in water baths of various temperatures, to either greater or lesser extents. The flexural strength and modulus followed a similar trend when immersed in water at ambient temperature. However, the contrary was true for composites when immersed in 60 and 100°C water baths. The impact strength increased after immersion in water at each immersion temperature, and the extent of such increment decreased with increasing the immersion temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2824–2832, 2002     

Effect of electron beam irradiation on physico–mechanical properties of wood flour–polyethylene composites

Agricultural lignocellulosic fiber (wood flour)‐waste was used to prepare composite materials through partial replacement of wood flour with low density polyethylene powder (LDPE) ranged from 10 to 20% by weight; these composites were made with and without electron beam irradiation (EB). The results obtained showed that, flexural strength, modulus of elasticity, modulus of rupture, and impact strength increase with increasing content of LDPE up to 20%. While, the percentages of thickness swelling and water absorption are decreased directly with increasing content of LDPE. Furthermore, the EB irradiation improves the physico‐mechanical properties of composite materials from 10 to 50 kGy. The results obtained are also confirmed by scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Impact strength improvement of wood flour–recycled polypropylene composites

In this research, the improvement of the impact strength of wood flour–recycled polypropylene (PP) composites through impact modification was studied. For this purpose, a virgin polypropylene (VPP) was thermomechanically degraded by five extrusions under controlled conditions in a twin‐screw extruder at a rotor speed of 100 rpm and a temperature of 190°C. PP (VPP and recycled PP at the second and fifth stages) and wood flour were compounded at 50 wt % wood flour loading in a counterrotating twin‐screw extruder in the presence different contents of ethylene vinyl acetate (EVA) to produce the wood flour–PP composites. From the results, the composites containing recycled PP exhibited significantly lower impact strengths. The addition of EVA up to 9 wt % increased the impact strengths of the composites made with PP recycled two and five times by about 63 and 41%, respectively. The composites containing VPP exhibited higher impact strengths than those containing recycled PP and EVA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dynamic mechanical properties of extruded nylon–wood composites

Dynamic mechanical properties determine the potential end use of a newly developed extruded nylon–wood composite in under‐the‐hood automobile applications. In this article, the dynamic mechanical properties of extruded nylon–wood composites were characterized using a dynamic mechanical thermal analyzer (DMTA) to determine storage modulus, glass transition temperature (T_g), physical aging effects, long‐term performance prediction, and comparisons to similar products. The storage modulus of the nylon–wood composite was found to be more temperature stable than pure nylon 66. The T_g range of the nylon–wood composite was found to be between 23 and 56°C, based on the decrease in storage modulus. A master curve was constructed based on the creep curves at various temperatures from 30 to 80°C. The results show that the relationship between shift factors and temperature follows Arrhenius behavior. Nylon–wood composites have good temperature‐dependent properties. Wood fillers reduced the physical aging effects on nylon in the wood composites. The comparison of the nylon–wood composite with other similar products shows that nylon–wood composites are a promising low cost material for industrial applications. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Mechanical and thermal flow properties of wood flour–biodegradable polymer composites

Wood flour (WF)–polycaprolactone (PCL) and polybutylenesuccinate–butylenecarbonate (PBSC) composites were prepared by knead processing. The effects of a compatibilizer on the tensile and thermal flow properties of the composites were investigated. PCL‐graft‐maleic anhydride (PCL‐g‐MA) was used as a compatibilizer. Tensile properties were improved by adding PCL‐g‐MA to both composites. The tensile strength and Young's modulus were increased from 13 to 27 MPa and 581 to 1011 MPa in WF–PCL (50/50, w/w) composites, respectively, and from 17 to 28 MPa and 814 to 1007 Mpa in WF–PBSC (50/50, w/w) composites, respectively, with the addition of 5% PCL‐g‐MA. Elongation at break increased from 4 to 7% and from 3 to 6% in the WF–PCL and the WF–PBSC composites, respectively. Tensile strength was further increased with increasing WF content in the presence of PCL‐g‐MA. Thermal flow temperature and melt viscosity of the composites were increased, and water absorption and thickness swelling were improved with the addition of PCL‐g‐MA. It was found from the burial test that all composites were more than 40% degraded within 6 weeks, and there was no considerable difference in degradation between composites with PCL‐g‐MA and those without. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1900–1905, 2003     

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     

Electrical conductivity and mechanical performance of multiwalled CNT‐filled polyvinyl chloride composites subjected to tensile load

This article reports a study on the strain‐sensitive conductivity (tensoresistivity) and mechanical properties of polyvinyl chloride/multiwalled carbon nanotube (PVC/MWCNT) composites subjected to tensile loading at different strain rates for potential use in sensor‐enabled geosynthetics and other applications involving electrically conductive polymer composites. Results indicate that adding 0.5 wt % MWCNT to the composite results in 57% reduction in its ultimate (failure) strain and a fivefold increase in its tensile modulus while leaving its ultimate strength almost unchanged. Laser scanning confocal microscopy is used to investigate the microscopic failure mechanism of the composite and how it contributes to the strain‐sensitive conductivity of the composites. It is observed that tensile fractures are initiated from inside the largest bundles between 18% and 36% strain and continue through further fractal‐like fracturing in smaller bundles. Gauge factors (e.g., 3.17) comparable to or exceeding those of typical strain gauges are obtained for the composite, indicating its strong potential for structural performance monitoring and damage detection applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43665.     

Amine treatment of polyvinyl chloride/wood flour composites

Ethanolamine and L ‐arginine treated wood flour were added to polyvinyl chloride (PVC) in order to improve the interphase between PVC and wood. The influence of the treatment on pH‐value changes and nitrogen fixation of the wood and mechanical properties of the composite were evaluated. The treatments changed the pH of wood from acidic to basic. The highest nitrogen fixation was measured for monoethanolamine and L ‐arginine treated wood flour at high concentrations. Tensile strength, elongation at break, and unnotched impact strength were improved by ethanolamine and L ‐arginine treatments considerably. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of highly degraded high‐density polyethylene (HDPE) on processing and mechanical properties of wood flour‐HDPE composites

The influence of highly degraded high‐density polyethylene (HDPE) on physical, rheological, and mechanical properties of HDPE‐wood flour composites was studied. For this purpose, the virgin HDPE was subjected to accelerated weathering under controlled conditions for 200 and 400 h. The virgin and exposed HDPE and pine wood flour were compounded to produce wood flour‐HFPE composites. The results showed that the accelerated weathering highly degraded HDPE. Degradation created polar functional carbonyl groups and also produced extensive cross‐linking in HDPE and consequently poor processibility. The interruptions in the flow characteristics of the degraded HDPE potentially caused processing hurdles when using them for extrusion or injection molding manufacturing as only small part (10%) of virgin HDPE could be replaced by highly degraded HDPE for wood flour‐HDPE composite manufacturing. The mechanical properties of composites containing highly degraded HDPEs were similar to the composites with virgin HDPE and in some cases they exhibited superior properties, with the exception being with the impact strength. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dynamic mechanical analysis of tropical wood–polymer composites

Wood–polymer composites (WPC) of Geronggang (GE; Cratoxylon arborescens), a light tropical hardwood, impregnated with methyl methacrylate (MMA) and styrene-co-acrylonitrile (3 : 2; STAN), were prepared by in situ polymerization using γ radiation or catalystheat treatment. The dynamic flexural storage modulus, E′, for oven-dried GE, moist GE, and GE–MMA and GE–STAN composites decreased with increasing temperature. The percentage decreases for GE with 10 and 16.5% moisture contents were 74.5 and 98.2%, respectively, which were higher than those for GE and GE composites, which ranged between 40 and 50%. The impregnated polymers were not as effective as water in acting as plasticizers, due to their nonpolar nature and much higher molecular weights. The α-transition peaks for moist GE and GE composites were more distinct and were shifted to lower temperatures than those for oven-dried GE. The values ranged between 75 and 150°C for moist GE and between 102 and 170°C for the GE composites. The α-transitions of the catalyst–heat-treated GE composites were lower than that of the radiation-induced counterparts. GE–STAN composites were also observed to have lower α-transition temperatures than those for GE–MMA for the respective treatment process, which seems to suggest that STAN interacted to a greater extent with cell wall components than did MMA.     

Thermal and mechanical properties of wood flour–polystyrene blends from postconsumer plastic waste

Polystyrene (PS) from packing materials and plastic cups was reinforced with 30 and 50% wood flour through a blending process with and without a commercial compatibilizing agent. The processability of the pure recycled polystyrene (rPS) and wood–rPS composites was studied in terms of the torque of the mixing process; this was then compared with that of a commercial virgin multipurpose PS. The physical and mechanical properties were compared with those of the virgin PS reinforced with 30 and 50% wood flour. The results show that the mechanical properties of the pure and reinforced rPS did not decrease with respect to the virgin PS, and in terms of the impact strength, the rPS was superior to the virgin plastic. The mechanical properties were not affected by the commercial compatibilizing agent, but the torque of the blends was significantly lower with the compatibilizer. Differential scanning calorimetry (DSC) and dynamic mechanical analysis were used to study the glass‐transition temperature (T_g) of both the pure virgin PS and pure rPS and the wood flour–PS composites. The T_g values of the rPS and wood–rPS composites were higher than those of the virgin PS and wood–virgin PS composites. The use of rPS increased the stiffness and flexural modulus of the composites. Thermogravimetric analysis revealed that the thermal stability of rPS and its composites was slightly greater than that of the virgin PS and its composites. These results suggest that postconsumer PS can be used to obtain composite materials with good mechanical and thermal properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of oxidized polypropylene as a new compatibilizer on the water absorption and mechanical properties of wood flour–polypropylene composites

The effect of oxidized polypropylene (OPP) as new compatibilizer on the water absorption and mechanical properties of wood flour–polypropylene (PP) composites were studied and compared with maleic anhydride grafted polypropylene (MAPP). The oxidation of PP was performed in the molten state in the presence of air. Wood flour, PP, and the compatibilizers (OPP and MAPP) were mixed in an internal mixer at temperature of 190°C. The amorphous composites removed from the mixer were then pressed into plates that had a nominal thickness of 2 mm and nominal dimensions of 15 × 15 cm² with a laboratory hydraulic hot press at 190°C. Physical and mechanical tests showed that the wood flour–PP composites with OPP exhibited higher flexural and impact properties but lower water absorption than MAPP. All of the composites with 2% compatibilizers (OPP and MAPP) gave higher flexural and impact properties and lower water absorption compared to those with 4% compatibilizers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical properties of teak wood flour‐reinforced HDPE composites

Mechanical properties such as tensile and impact strength behavior of teak wood flour (TWF)‐filled high‐density polyethylene (HDPE) composites were evaluated at 0–0.32 volume fraction (Φ_f) of TWF. Tensile modulus and strength initially increased up to Φ_f = 0.09, whereas a decrease is observed with further increase in the Φ_f. Elongation‐at‐break and Izod impact strength decreased significantly with increase in the Φ_f. The crystallinity of HDPE also decreased with increase in the TWF concentration. The initial increase in the tensile modulus and strength was attributed to the mechanical restraint, whereas decrease in the tensile properties at Φ_f > 0.09 was due to the predominant effect of decrease in the crystallinity of HDPE. The mechanical restraint decreased the elongation and Izod impact strength. In the presence of coupling agent, maleic anhydride‐grafted HDPE (HDPE‐g‐MAH), the tensile modulus and strength enhanced significantly because of enhanced interphase adhesion. However, the elongation and Izod impact strength decreased because of enhanced mechanical restraint on account of increased phase interactions. Scanning electron microscopy showed a degree of better dispersion of TWF particles because of enhanced phase adhesion in the presence of HDPE‐g‐MAH. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal and mechanical properties of polypropylene–wood powder composites

The preparation and characterization of modified and unmodified polypropylene (PP)–wood powder (WP) composites were done under fixed processing conditions. Different techniques were used to study the effect of both WP size and content, as well as compatibilizer content, on the properties of the composites. The results point to the fact that, WP settles in the amorphous part of the matrix and creates new crystalline phases or zones. Scanning electron microscopy micrographs show a relatively even distribution of WP in the PP matrix, which contributes to improvements observed in the properties of the material. Hg‐porosimetry results indicate that the PP matrix, which has a low pore volume, filled the pores in the WP particles. This reduced the total volume of pores in the PP–WP composites. This observation was also supported by a general decrease in gas permeability of the material. Thermal analysis results indicate that the presence of both WP and maleic anhydride grafted polypropylene (MAPP) leads to an increase in enthalpy (crystallinity) values, but to a decrease in lamellar thickness in the composites. The thermal stability of the composites improves somewhat compared to that of PP. There were distinctive differences between the results for composites containing different WP particle sizes, as well as for composites prepared in the presence and absence of MAPP. It is clear from the results that the presence of MAPP generally improves the tensile properties of the composites. Larger WP particles gave rise to better tensile properties, in the presence and absence of MAPP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4173–4180, 2006     

Dynamic mechanical behavior of highly filled polymers: Dewetting effect

This paper describes the results of simultaneous dynamic measurements in tension and torsion made on propellant samples. The complex dynamic moduli E′, E″, G′, and G″ at low frequencies were determined within a temperature range from room temperature to ?90°C. Time temperature shift factors and reduced master curves for both tension and shear properties are discussed. The effect of dewetting on the dynamic properties in tension and shear was also investigated. A preliminary attempt is made to compute the degree of dewetting in a propellant by applying Beer-Lambert's law.     

Influence of various wood modifications on the properties of polyvinyl chloride/wood flour composites

Aminosilane, melamine and acetic anhydride treated wood flour were added to polyvinyl chloride (PVC) in order to process improved PVC/wood flour composites. The influence of wood treatment on water absorption and mechanical properties were evaluated. Treatments with amino-alkyl functional oligomeric siloxane and melamine in suitable concentration as well as acetylated wood flour composites showed decreased equilibrium moisture content and reduced speed of water absorption. Tensile strength, elongation at break and unnotched impact strength were considerably improved by the aminosilane treatments. The increase in strength and elongation was mainly influenced by the chemical structure and concentration of the used aminosilanes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Starch‐filled ternary polymer composites. I: Dynamic mechanical properties

The dynamic mechanical properties of starch‐filled blends of polyethylene (PE) and poly(hydroxy ester ether) (PHEE) are strongly dependent on the properties and distribution of the minor component (PHEE). The effect of the minor component on the viscoelastic properties was investigated by modeling the storage modulus. G′, using a step‐wise homogenization process. A comparison of theoretical and experimental data indicates that the morphology changes as the total volume fraction of filler ?_t, increases. At low ?_t, the PHEE encapsulates isolated starch granules. Above ?_t, ～ 0.2, the PHEE surface coating contributes to the formation of particle clusters. Evidence of particle encapsulation was provided by a microscopic examination of fractured tensile bars. At all filler contents, the decrease in the composite's modulus at the T_g of PHEE is larger than can be accounted for if this material is simply dispersed in the matrix. When the starch granules are clustered, the decrease is also too large to be accounted for by only considering particle encapsulation. The effect of particle clustering must be included in order for the model to correctly describe the temperature dependence of the storage modulus.     

Effects of the accelerated freeze‐thaw cycling on physical and mechanical properties of wood flour‐recycled thermoplastic composites

This study investigated durability performance of wood‐plastic composites (WPCs) that were exposed to accelerated cycling of water immersion followed by freeze thaw (FT). The WPCs used in this study were made of high‐density polyethylene (HDPE) or polypropylene (PP) with radiata pine (Pinus radiata) wood flour using hot‐press molding. These two types of plastics included both recycled and virgin forms in the formulation. In the experiments, surface color, flexural properties, and dimensional stability properties (water absorption and thickness swelling) were measured for the FT cycled composites and the control samples. Interface microstructures and thermal properties of the composites were also investigated. The results show that the water absorption and the thickness swelling of the composites increased with the FT weathering. In the meantime, the flexural strength and stiffness decreased. Scanning electron microscopy (SEM) images of the fractured surfaces confirmed a loss of interface bonding between the wood flour and the polymer matrix. Differential scanning calorimetry (DSC) showed a decrease in crystallization enthalpy and crystallinity of the wood flour‐plastic composites as compared with the neat PP and HDPE samples. The crystallinity of the FT cycled composites using the virgin plastics (vPP and vHDPE) increased; however, the composites with the recycled plastics decreased in comparison with corresponding control samples. In general, the properties of the composites were degraded significantly after the accelerated FT cycling. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers