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The water transport kinetics and moisture-induced thickness swelling behavior of wood-plastic composites (WPCs) in the presence of two imidazolium-based ionic liquids (ILs) were studied. The wood flour chemically treated with ILs were compounded through melt mixing of high-density polyethylene and coupling agent, and finally, the test specimens were produced by compression molding. Hygroscopic rates of the composites were evaluated by immersing them in the water at room temperature and monitoring moisture sorption and thickness changes for several weeks. Besides, the water diffusion coefficients and swelling rate parameters were measured for all composites. It was found that the water absorption and thickness swelling of the WPC specimens reduced as a result of ILs treatment. The SEM analysis revealed that the presence of ILs can improve the quality of adhesion between the polymer matrix and the cellulosic materials, to decrease the gaps in the interfacial region and block the hydrophilic groups. Studying the water sorption process in the specimens showed that the process follows kinetics and mechanisms described by Fick’s law. The highest water diffusion coefficients and swelling rate parameters were found in composites with untreated wood.

The nanocomposites of high-density polyethylene, low-density polyethylene, polypropylene, and poly(vinyl chloride) reinforced with Azadirachta indica wood flour (WF) and different amounts of the organomodified nanoclay and titanium dioxide (TiO2) nanopowder were produced by melt-blending process followed by compression molding. Polyethylene- co-glycidyl methacrylate (PE- co-GMA) was used as a compatibilizer. TiO2 nanopowder was synthesized by sol–gel method and characterized using transmission electron microscopy (TEM). The average size of the synthesized nano-TiO2 was 17.5 nm, which was confirmed both by TEM and X-ray diffraction (XRD) study. The distribution of nanoparticles in the nanocomposites was also examined by the XRD study. The surface modification of the TiO2 nanoparticles by organic surfactant cetyl trimethyl ammonium bromide and their interaction with the wood and the polymer were studied by Fourier transform infrared spectroscopy. Incorporation of compatibilizer PE- co-GMA, nanoclay, and nano-TiO2 significantly influenced the mechanical and thermal properties of the WF-reinforced composites. Wood polymer composites (WPC) reinforced with nanoclay and nano-TiO2 showed improved tensile strength, tensile modulus, flexural strength, flexural modulus, and hardness. Maximum improvement in mechanical properties was shown by WPC loaded with 40 phr WF, 2 phr nanoclay, and 2 phr of nano-TiO2. On inclusion of organically modified nanoclay and nano-TiO2, the WPC samples showed lower water uptake and higher chemical resistance. The nanocomposites were further examined by TEM study and thermogravimetric analyzer.

This study emphasizes on closed-loop recycling of wood flour/poly (vinyl chloride) composites, since there is normally a considerable amount of material waste in wood plastic production lines. Composite materials were produced and subjected to four times reprocessing cycles under industrial conditions. Detailed analytical methods including bending strength, modulus of elasticity, impact strength, scanning electron microscopy, fiber length, water absorption, contact angle, Fourier transform infrared, and dynamic mechanical thermal analysis (DMTA) were conducted to evaluate the effects of recycling on the mentioned composites. Results demonstrated that the recycled composites, except for the four-time recycled ones, had lower bending strength, modulus of elasticity, and impact strength due to fiber-chain scission/fracture resulting from shear stress during reprocessing; however, impact strength remained almost unchanged after the first recycling cycle. Results also revealed that generally the reprocessed composites showed lower water absorption rates due to better fiber wetting and encapsulation. There was also a reduction in hemicellulose hydroxyl groups, rendering the recycled composites less hydrophilic. DMTA results showed an increase in mechanical loss factor (tan δ) for all the reprocessed composites showing a more viscous than elastic nature. The glass transition temperature of Rec4 composites increased due to polymer dehydrochlorination and the resulting cross-linking, which restricted the molecular mobility of the polymer chains.

Waste from the maintenance of electricity distribution networks is generated every day, in repairing and replacement of components used in electricity distribution networks. Among the most dangerous residues, wood poles treated with chromated copper arsenate are distinguished by the toxicity of the chemical treatment it has been submitted to, as well as its ceramic insulators, due to the difficult recyclability of this material. Thus, an alternative may be the reuse of these components as reinforcing elements in polymeric composites. Based on this, two residues were used as fillers for the production of high-density polyethylene (HDPE) hybrid composites, wood powder, and insulating ceramic powder. Degradation by ultraviolet (UV) exposure in controlled environments of the composites was also evaluated, and toxicity tests were carried out based on the leaching of these loads with increased exposure time to degradation. Composites presented higher tensile and flexural properties than pure HDPE, and after the exposure to the UV degradation process, the composites presented fewer cracks when compared to HDPE. After exposure to the simulated degradation environment, the levels of chromium, copper, and arsenic leached were within the limits allowed by the standard that provides classification and means of disposal of these materials.

In this study, composites with interesting mechanical and thermal properties were prepared using chemically modified vegetable oil as coupling agent in wood-fibers-reinforced recycled polypropylene. Soybean oil was reacted with maleic anhydride to produce maleated soybean oil (MASO). The mechanical, thermal, and morphological properties of the composite were evaluated. The usage of MASO as a coupling agent clearly improved the interfacial adhesion between wood fibers and the polypropylene matrix and increased the mechanical and thermal properties evaluated. Based on the obtained results, it is concluded that MASO can act as an alternative source of coupling agent dispensing with the addition of petroleum-based compatibilizers to improve the mechanical and thermal properties of composites reinforced with natural fibers.

Polypropylene (PP)/wood flour/fiber (WF) composites with strong interfacial compatibility were prepared, and properties of the composites were studied. First, the wood fiber was surface modified by alkali treatment—this process is also termed as fibrillation that creates rough surface, cavities, and much interspace between smaller fibrils. Then multi-monomer grafted copolymers of PP (MPP-St) and PP wax (MPPW-St) were synthesized. The so synthesized MPP-St/MPPW-St well compatibilized the interfaces of the PP/alkali-treated WF (TWF) composites. Mechanical property and water resistance results demonstrated that synergistically compatibilized PP/TWF composites had a better performance than composites compatibilized by MPE-St or MPPW-St separately, uncompatibilized composites, and PP/untreated wood flour (UWF) composites. The interfacial structures of all these composites were characterized by scanning electron microscopy. A three-dimensional mold was constructed to reveal that MPP-St affords a strong interfacial interaction between PP and rough surface of treated fiber, while MPPW-St supplements the interfacial interaction by permeating into the interspace between smaller fibrils of alkali-treated fiber. The mold fitted the results very well.

This study extensively investigated the surface roughness of injection molded wood plastic composites (WPCs) produced from different amounts of wood flour, polymer matrix, mineral filler, and other additives. A larger range of roughness parameters that used in the previous literature were obtained from nine different WPC compositions by using a robust filtering method (robust Gaussian regression filter) to have a better understanding of the overlaying quality of the WPC samples. Three melt flow index (MFI) of the polymer were tested (MFI 3.6, 12, and 25). It was found that WPCs produced with the polypropylene having a MFI value of 25 were the smoothest. It was noticed that not only the wood flour percentage matters but the combination of wood flour–mineral filler was also important. The WPC compositions with lower polymer amount in favor of more wood flour and mineral filler led to rougher surfaces. A decrease of wood flour in favor of increasing the mineral filler participation percentage had a surface smoothing effect. At the same wood flour content, a decrease in polymer combined with an increase in mineral filler led to rougher WPC surface. Among the tested WPC compositions, the smoothest surface was obtained in the specimens produced from 50% wood flour, 0% mineral filler, and around 40% polymer by weight. The results should be helpful to anticipate the effect on surface roughness of the percentage participation for each amount of the wood or mineral filler, polymer matrix, and additives in further development of WPC combinations.

In this research, the effects of foaming and of nanoclay on foam morphology and soundproofing of wood flour/low-density polyethylene (LDPE) composites were investigated. For this purpose, LDPE, wood flour, foaming agent, and nanoclay were mixed in an internal mixer to produce test samples. The standard circular samples were made using compression molding method in a hot press machine. Sound transmission loss (STL) was measured by an impedance tube. Results showed that foaming and nanoclay increase the STL of the composites at frequencies above 2000 Hz. The biggest increase in STL has been found for the foamed composites containing nanoclay. The addition of nanoclay decreased the average cell size and increased the cell density of foamed composites.

The present work investigates the effect of jack wood flour (JWF) content on the fracture toughness, tensile, impact, and morphological behavior of the prepared green biocomposites. From 0 to 35 wt% (volume fraction ( Φf) = 0–0.34) of JWF was incorporated as a reinforcing biodegradable filler into poly(ε-caprolactone) (PCL) matrix by melt compounding in a twin screw extruder. The tensile modulus increases by 80.48% at the highest Φf= 0.34, though marginal increment (13.71%) in the yield strength was registered. A sharp reduction in notched Izod impact strength (85%) was observed with increasing JWF content. The fracture toughness of the prepared biocomposites based on post-yield fracture mechanics concept was investigated by essential work of fracture (EWF) methodology. Incorporation of JWF into PCL matrix diminishes the EWF ( we), while increasing the non-essential work of fracture ( βwp). In the biocomposites, principally two mechanisms governed the fracture deformation. Large JWF particles act as stress concentration points and favor the crack initiation, while the smaller particles favor fibrillation which arrests the crack propagation enhancing the parameter βwpat lower concentration of JWF. Freeze-fractured surfaces show a degree of phase adhesion at lower Φfof JWF. The phase adhesion parameter obtained from micromechanical analysis of tensile properties suggesting the mechanical interlocking and interaction between PCL and JWF.

This experimental work is aimed at studying the effect of fiber surface modification including alkaline, acetic acid, and benzyl chloride on the long-term water absorption and thickness swelling (TS) of wood flour (WF)-reinforced polypropylene composites. The samples were made by melt compounding and then injection molding. Hygroscopic rates of the samples were evaluated by immersing them in water at room temperature and monitoring moisture sorption and thickness changes for several weeks. The results indicated that chemical modification has a significant effect on the water absorption of composites. The mechanism of water absorption of all samples followed the kinetics of a Fickian diffusion process. The composites modified with acetylation-treated fiber showed the lowest and the unmodified composites exhibited the highest water absorption coefficient. TS of the composites was clearly dependent upon the WF chemical modification. The swelling rate parameter of treated samples is less than those of untreated ones.

Poly(lactic acid) (PLA) and wood flour/PLA composites were prepared and blended with two antimicrobial agents, triclosan and silver-substituted zeolite (Zeomic), using a twin-screw extruder. The mechanical and thermal properties, antimicrobial activity, and biodegradation performance were investigated. The addition of wood and Zeomic was found to increase the Young’s modulus of the composites, whereas the tensile strength, elongation at break, and impact strength dropped. However, the mechanical properties of PLA and wood/PLA loaded with triclosan did not show any definite trends. Differential scanning calorimetry data indicated that the glass transition temperature value of neat PLA was 63°C, whereas those of wood/PLA composites were lower. When wood and Zeomic were incorporated, PLA exhibited double melting peaks. Triclosan (1.0 and 1.5 wt%) demonstrated antibacterial activity against Staphylococcus aureus, as determined by plate count agar technique, whereas Zeomic did not. Biodegradation tests of neat PLA and wood/PLA composites showed that after a 60-day incubation period, the biodegradation rate of wood/PLA was higher than that of PLA. PLA and wood/PLA-containing Zeomic were found to degrade more quickly, suggesting that wood and Zeomic acted as biodegradation promoters. On the other hand, triclosan could be considered a biodegradation retarder since no biodegradation was observed for any triclosan-loaded samples during the initial 20 days of incubation, while neat PLA and wood/PLA composites began to degrade within the first few days.

In this article, the different chemical modifications of natural fiber on the physical and mechanical properties of polypropylene (PP)/wood flour (WF)/nanoclay hybrid composites were studied. To meet this objective, the chemical treatments on WF, namely alkali, acetylation, and benzoylation, were carried out. Then, the composites were prepared through the melt mixing of WF and PP at 50% weight ratios, with various amounts of nanoclay (0, 3, and 6 per hundred compounds (phc)) in Haake internal mixer and the test specimens were prepared by injection molding. The amount of coupling agent was fixed at 2 phc for all formulations. The tensile strength, impact strength, and water uptake of these composites were analyzed and the reinforcing properties of the chemically treated composites were compared with those of untreated composites. The chemical modification efficiency was verified by Fourier transform infrared (FTIR) analysis, and the dispersion state of nanoclay in the composites was examined using X-ray diffractometer and transmission electron microscopy. The results showed that the tensile modulus, tensile strength, and impact strength of the composites increased by applying chemical treatments. Modified composites had lower water absorption (WA) and thickness swelling than unmodified ones. Furthermore, the highest mechanical properties and the lowest water uptake were observed in the composite modified with acetic anhydride. FTIR spectra show that the intensity of O–H bond at 3444.2 cm–1 and formation of ester bond at 1741.4 cm–1 were indications of changes in the chemical structure of the fibers. The tensile modulus and strength increased with increase of nanoclay up to 3 phc and then decreased. However, the impact strength and WA decreased with increase of nanoclay loading. The morphological findings showed that the samples containing 3 phc of nanoclay had higher order of intercalation and better dispersion.

The present study aims to investigate the moisture absorption of polypropylene (PP)/rubberwood flour (RWF) composites and its effects on dimensional stability. The compositions included different grades of plastic, and the amounts of wood flour, maleic anhydride-grafted polypropylene (MAPP), and ultraviolet (UV) stabilizer were varied. The composite materials were manufactured into panels by a twin-screw extruder. Long-term water absorption (WA), long-term thickness swelling (TS), and degradation of flexural properties of the composites were studied for a range of water immersion times. The WA and TS of the samples increased with RWF content and immersion time. Recycled PP gave higher WA and TS than virgin PP, for the composites with 45 wt% RWF. Increasing MAPP content from 3 to 5 wt% had no significant effect on WA and TS, whereas the addition of 1 wt% UV stabilizer increased them. A MAPP content of 3 wt% is recommended for moisture resistance, while the amount of UV stabilizer should be kept as low as possible. Flexural strength and modulus of composites also decreased with moisture uptake; however

In this study, the effect of multi-walled carbon nanotubes (MWCNTs) and maleic anhydride-grafted polyethylene (MAPE) on the physical and mechanical properties of composites based on wood flour (WF) and high-density polyethylene (HDPE) was investigated. To meet this objective, MWCNTs, as a reinforcing agent, in 4 levels of 0, 1, 3, and 5 wt% and MAPE, as a compatibilizer, in 2 levels of 0 and 3 wt% were used. The amount of WF was fixed at 50 wt% for all formulations. First, the materials were prepared by melt compounding process in an internal mixer (Brabender® Plasti-Corder®), and then the samples were manufactured by injection molding method. The morphology of the specimens was characterized using scanning electron microscopy (SEM) technique. The results showed that when the contents of the MWCNTs were increased from 0 to 3 wt%, the tensile strength and modulus of the samples increased to 41.7% and 24.3%, respectively, and the water absorption values of the samples decreased to 58.8%. Similar results were also observed for the thickness swelling values. Both mechanical and physical properties of samples were improved by adding MAPE up to 3 wt%. The nanocomposites having 3 wt% MWCNTs and 3 wt% MAPE exhibited the highest impact and tensile strength values, while tensile modulus and physical properties reached their maximum when 5 wt% of MWCNT and 3 wt% of MAPE were used. Also, SEM micrographs showed that CNTs can fill the voids of wood–plastic composites, and the addition of MAPE and MWCNTs enhanced the interaction between the components.

Paulownia wood flour (PWF), a by-product of milling lumber, was employed as a biofiller and blended with high-density polyethylene (HDPE) via extrusion. Paulownia wood (PW) shavings were milled through a 1-mm screen and then separated via shaking into various particle fractions (600–≤74 µm) using sieves (#30–>#200 US Standards). The influence of a commercial coupling agent, maleated polyethylene (MAPE), used at various concentrations (0, 1, 3, 5, or 10% w/w) with HDPE and wood particles obtained from a #50-mesh sieve, is examined. Incorporation of high concentrations of MAPE (approximately 5%) in HDPE-PWF blends improved tensile strength compared to lower MAPE concentrations (≤3%). Particle size of wood significantly influenced the mechanical properties of the biocomposite. HDPE-MAPE blends containing smaller wood particles (300 µm). Young’s modulus for all HDPE-PWF-MAPE blends was 14–27% higher than that of neat HDPE. Generally, incubation of tensile bars of various HDPE-PWF blends in 95% humidity for 28 days reduced the mechanical properties approximately by 5%. Differential scanning calorimetry analysis showed a slight reduction in the percentage crystallinity among various HDPE-PW blends.

In this study, the effect of organomodified montmorillonite (OMMT) on the acoustic properties and clay dispersion of polypropylene (PP)/wood flour (WF) composites was investigated. To meet this objective, the blend composites were prepared through the melt mixing of PP/WF at 50% weight ratios, with various amounts of OMMT (0, 3, and 6 per hundred compounds (phc)) in hake internal mixer then the samples made by injection molding. The amount of coupling agent was fixed at 2 phc for all formulations. The acoustic properties such as speed of sound propagation, time of sound propagation, and sound energy absorbance were evaluated. Results indicated that the time of sound propagation and sound energy absorbance of composites increased with increase in OMMT. However, the speed of sound propagation decreased with the increase in OMMT loading. Also, the biggest improvement of the tensile modulus can be achieved for the nanoclay loading at 3 phc. X-Ray diffraction patterns and transmission electron microscopy revealed that the nanocomposites formed were intercalated. Also, morphological findings showed that samples containing 3 phc of OMMT had higher order of intercalation.

Wood polymer composite (WPC) was prepared using solution-blended high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), poly(vinyl chloride) (PVC), wood flour (WF) and polyethylene- co-glycidyl methacrylate (PE- co-GMA). The effect of nanoclay, SiO2 and ZnO addition on the properties of the composite was examined. The distribution of silicate layers, SiO2 and ZnO nanopowder was studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The improvement in miscibility among polymers was studied by scanning electron microscopy (SEM). Fourier transform infrared spectroscopic (FTIR) studies reveal the interaction between polymer, wood, clay, SiO2 and ZnO. WPC treated with 3 phr each of clay, SiO2 and ZnO showed an improvement in mechanical properties, thermal stability and a decrease in water uptake capacity.

This research explores the effects of chemical foaming agent and nanoclay on the long-term water absorption and cell morphology of wood–plastic nanocomposites. To meet this objective, the nanoclay, high-density polyethylene, and coupling agent were compounded and then granulated and were mixed with wood flour and blowing agent in a twin-screw extruder. Consequently, foaming process was completed in injection stage. The amount of wood flour was fixed at 50 wt% for all the samples. For nanoclay and chemical blowing agent, different levels of 0, 2 and 4 per hundred resins (phr) and 0, 0.5, 1 and 1.5 phr were considered, respectively. The long-term water absorptions of samples were evaluated by immersing them in water for several weeks, and water diffusion coefficients were also calculated by evaluating the water absorption isotherms. Results indicated that the water absorption, cell size, and average cell density of composites increased with increase in chemical foaming agent loadings. However, by the addition of nanoclay to wood–plastic composite foams, the water absorption and cell size decreased and their cell density increased. Scanning electron microscopy confirmed that the chemical foaming agent and nanoclay contents had significant influence on density reduction in foamed composites. X-Ray diffraction patterns revealed that the nanocomposites formed were intercalated. The mechanism of water absorption of the foamed wood–plastic nanocomposites under study followed the kinetics of a Fickian diffusion process.

This study investigates the effect of nanoclay on the cell morphology and thickness swelling behavior in the extrusion foaming of wood flour/polyethylene composites with a chemical blowing agent. To meet this objective, the nanoclay, high-density polyethylene, and coupling agent were compounded and then the granules were mixed with wood flour and blowing agent in a twin-screw extruder. Consequently, foaming process was completed in the injection stage. The amount of wood flour was fixed at 50 wt% for all samples. For nanoclay and chemical blowing agent, different levels of 0, 2, 4 per hundred resins (phr) and 0, 0.5, 1, 1.5 phr were considered, respectively. The results indicate that the addition of clay generally reduces the cell size, increases the cell density, and facilitates foam expansion. Furthermore, the thickness swelling of the composite decreased with increase in nanoclay. The composites containing 1.5 phr of foaming agent exhibited higher thickness swelling value and swelling rate parameter ( KSR) than those containing nanoclay. The swelling model provided a good predictor of the hygroscopic thickness swelling process of wood flour/polyethylene/nanoclay hybrid foamed composites.

Wood-plastic composite (WPC) can be fine-cell processed to create a new class of low-weight composite material with improved mechanical properties that could broaden their applications. This study investigated the effects of a chemical blowing agent (CBA) and the drawdown ratio (DDR) on the surface quality, cell morphology, and mechanical properties of extruded foamed WPC profiles. The rectangular foamed WPC profiles were produced from high-density polyethylene and wood flour with different CBA contents and DDR values using a twin-screw extrusion line. The foam density, cell density, and their sizes and shapes were largely depended on the CBA content and the DDR. A foamed WPC profile with a 22% density reduction with cellular structure can be produced using an extrusion profile line.

The scope of the present article is to study the effect of reinforcing filler loading and coupling agent treatment on long-term water uptake of wood plastic composites. Polypropylene and wood flour were compounded into hake internal mixer and the test specimens were prepared by injection molding. Three different contents of wood flour as 40%, 50% and 60% were considered, and the concentration was varied from 0 to 4% for coupling agent. The long-term water absorptions of samples were evaluated by immersing them in water at room temperature for several weeks, and water diffusion coefficients were also calculated by evaluating the water absorption isotherms. The results showed that the water absorption in the samples increased with immersion time, reaching a certain value at saturation point and the composites water content remained constant. Also, the water absorption of the composites increased with increasing wood flour loading. The coupling agents had a positive effect on the water absorption of these composites. Water absorption of all formulations approached the Fickian diffusion case.

The wood plastic composites (WPCs) are made using matrices of recycled polypropylene with sawdust (pine wood flour) as filler. Corresponding WPCs are also made using virgin plastics (vPP, virgin polypropylene) for comparison with the recycled plastic-based composites. All varieties of these WPCs are made through melt compounding and injection molding with varying formulations based on the plastic type (PP, polypropylene), plastic form (recycled and virgin), wood flour content, and addition of maleated polypropylene-coupling agent. The melt flow index and mechanical properties of WPCs are investigated. The results clearly show that recycled PP (rPP) can be successfully used to produce stable and strong WPCs. Properties and performances of WPC made of rPP are comparable to WPC made of wood and vPP. Therefore, WPCs based on both rPP and vPP matrices have potential to be used as construction materials with wood flour.

Polypropylene (PP) hybrid composites filled with wood flour (WF) and short glass fiber were prepared by melt blending and injection molding. Maleic anhydride-grafted PP (PP-g-MA), glycidyl methacrylate-grafted PP (PP-g-GMA), maleic anhydride-grafted ethylene-octene copolymer (POE-g-MA), and maleic anhydride-grafted hydrogenated styrene-butadiene-styrene (SEBS-g-MA) were used as the compatibilizers to enhance the interfacial adhesion between PP and the fillers. The effect of the types and contents of graft polymer on the crystallization and melting behavior, micromorphology, mechanical property, moisture resistance, and thermal stability of PP hybrid composites was observed. The result showed that PP-g-MA and PP-g-GMA had strong heterogeneous nucleation and promotion effect on PP crystallization. PP-g-MA was superior to enhance the tensile, flexural, and impact properties of composites. Hybrid composites had excellent moisture resistance and low water absorption. WF and PP macromolecular compatibilizer could improve the thermal stability of PP composites, in which the most obvious effect was obtained in PP-g-MA-modified WF and short glass fiber hybrid system. As a result, PP/WF composite could achieve outstanding improvement effect by being modified with macromolecular compatibilizer.

The effect of filler addition and coupling agent content on the mechanical properties and morphology of wood plastic composites was examined. Using wood flour as the reinforcement filler and recycled expanded polystyrene as the thermoplastic matrix polymer, a particle-reinforced composite was prepared using a co-rotating twin-screw extruder. In the sample preparation, four levels of filler loading (10, 20, 30, and 40 wt%) and three levels of coupling agent content (1, 2, and 4 wt%) were used. The influence of particle size and particle morphology was also evaluated. The results showed that short fibers provide a higher specific surface area, enlarging the contact surface area with the polymer matrix. A wood flour loading of more than 20 wt% caused a decrease in the mechanical properties studied. The addition of 2 wt% of coupling agent improved the interfacial adhesion between the polymer matrix and wood flour and increased the flexural and impact strengths of the lignocellulosic composites. Addition of a coupling agent content greater than 2 wt% caused a reduction in the mechanical properties evaluated. A morphological study revealed that the positive effect of coupling agent on the interfacial adhesion of wood flour reinforced the expanded polystyrene composites.

Wood plastic composite (WPC) development has been facilitated by the economical extrusion of WPC profiles for various applications. The physical and mechanical properties of WPC products can be optimized by regulating extrusion processing conditions and material formulations. Rectangular WPC profiles were produced with varied high-density polyethylene (HDPE), wood fiber (WF), and lubricant contents under different extrusion conditions in a twin-screw extruder extrusion line. Optimal tensile and flexural properties were obtained with 50 wt% WF at 7 and 3 wt% lubricant and maleated polyethylene (MAPE) contents. The apparent shear viscosity of the WPC melts decreased gradually with increased lubricant content. Hence, for practical applications, a combination of HDPE grade, WF, lubricant, and MAPE contents can provide the benefits of lower shear viscosity while maintaining the mechanical properties and surface smoothness of WPC profiles.

The objective of the present article was to study the thermal degradation behavior of natural fiber polypropylene composites. Composite materials composed of 50% various natural fibers (wood flour, rice hulls, newsprint, and kenaf fibers) and polypropylene were studied using thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The effect of compatibilzer on the thermal stability of the composites was also evaluated. Contributions of components of one composite formulation to thermal degradation were also evaluated. It was found that among natural fibers, rice hulls were the least thermally stable ones in a polypropylene matrix. The compatibilizer slightly reduced thermal stability while enhancing fiber—matrix interaction and fractional crystallinity. The overall thermal degradation profile of the composite materials was found to be a more or less arithmetic average of those of the components.

In this study the influence of filler particle size (40, 50, and 60 meshes) and coupling agent concentration (0 and 2 wt%) on the composite mechanical properties were studied. Specimens having 30 wt% wood flour of poplar were mixed with polypropylene and polypropylene grafted maleic anhydride (PP-g-MA) as coupling agent. It was found that strength properties of the composites can be improved moderately by adding 2 wt% PP-g-MA. It was also observed that smaller filler particles provide higher tensile modulus than the larger sized filler. Moreover, increase in aspect ratio of the wood particles contributed to the enhancement in the mechanical properties of the composites. The elongation value was not found to have any considerable variation with particle size. The PP-wood flour composites exhibited low impact strength compared to pure PP. In general, Wood flour could be considered as a potential source of low cost, natural fibers for composites.