Effects of wood flour and chitosan on mechanical,chemical, and thermal properties of polylactide

Composites of polylactide (PLA, 100–60 wt%) and wood flour (0–40 wt%) were prepared to assess the effects of wood filler content on the mechanical, chemical, thermal, and morphological properties of the composites. The polysaccharide chitosan (0–10 wt%) was added as a potential coupling agent for the PLA‐wood flour composites. Addition of wood flour significantly increased the flexural modulus and the storage modulus of PLA‐wood flour composite, but neither the wood flour nor chitosan had an effect on the glass transition temperature (T_g). Fourier transform infrared spectra did not show any evidence of covalent bonding, but chitosan at the interface between wood and PLA is thought to have formed hydrogen bonds to PLA‐carbonyl groups. SEM images of fracture surfaces showed that fiber breakage was far more common than fiber pullout in the composites. No evidence of discrete chitosan domains was seen in SEM micrographs. When added at up to 10 wt% (based on wood flour mass), chitosan showed no significant effect on the mechanical, chemical, or thermal properties of the composites, with property changes depending on wood flour content only. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.     

Effects of copper amine treatment on mechanical properties of PVC/wood‐flour composites

Copper amine–treated wood flour was added to PVC [poly(vinyl chloride)] matrix in order to manufacture PVC/wood‐flour composites. Effects of copper treatments on the mechanical properties of PVC‐wood composites were evaluated. Unnotched impact strength, flexural strength, and flexural toughness of the composites were significantly improved by the wood‐flour copper treatment. The optimum copper concentration range was 0.2 to 0.6 wt% of wood flour. Fractured surfaces were examined by using scanning electron microscopy (SEM) combined with energy‐dispersive spectroscopy (EDS). PVC/wood interfacial debonding was the main fracture mode of untreated wood‐flour composites, whereas wood‐particle pullout and breakage dominating the fractured surfaces of copper‐treated wood‐flour composites. On the fractured surfaces, more PVC could be found on the exposed copper‐treated wood particles than on untreated wood, a result suggesting improved PVC‐wood interfacial adhesion after copper treatments. J. Vinyl Addit. Technol. 10:70–78, 2004. © 2004 Society of Plastics Engineers.     

Coextruded PVC/wood‐flour composites with WPC cap layers

Wood‐plastic composites (WPCs) can absorb moisture in a humid environment owing to the hydrophilic nature of the wood, thereby making the products susceptible to microbial growth and loss of mechanical properties. In this study, rigid poly(vinyl chloride) (PVC)/wood‐flour composites (core layer) were coextruded with either unfilled rigid PVC (cap layer) or rigid PVC filled with a small amount (5–27.5%) of wood flour (composite cap layers) in order to decrease or delay the moisture uptake. The thickness of the cap layer and its composition in terms of wood flour content were the variables examined during coextrusion. Surface color, moisture absorption, and flexural properties of both coextruded and noncoextruded (control) composite samples were characterized. The experimental results indicated that both unfilled PVC and composite cap layers can be encapsulated over rigid PVC/wood‐flour composites in a coextrusion process. The moisture uptake rate was lower when a cap layer was applied in the composites, and the extent of the decrease was a strong function of the amount of wood flour in the cap layer but insensitive to cap layer thickness. Overall, coextruding PVC surface‐rich cap layers on WPCs significantly increased the flexural strength but decreased the flexural modulus as compared with those of control samples. The changes in bending properties were sensitive to both cap layer thickness and wood flour content. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Evaluation and optimization of the mechanical properties of highly filled PVC/(wood flour) composites by using experimental design

In this study, PVC/(wood flour) (WF) composites were prepared by using a counterrotating twin‐screw extruder, and the effects on the mechanical properties of concentration and particle size of the WF, type and amount of coupling agent, K value of PVC, feed rate of extruder, and die temperature were investigated. Optimization of various formulation parameters based on the Taguchi method demonstrated that the wood content and wood particle size were the most important parameters. Flexural modulus increased upon increasing WF loading up to 50 wt%. Also, flexural strength and modulus increased with particle size because of the higher aspect ratio and better quality of mixing. Use of coupling agents had a minor effect that was attributed to the moderately high polarity of PVC causing relatively good compatibility between WF particles and the PVC matrix. The optimum level of WF calculated by considering the contribution factor was 50 wt%. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Wood‐fiber/high‐density‐polyethylene composites: Coupling agent performance

The coupling efficiency of seven coupling agents in wood–polymer composites (WPC) was investigated in this study. The improvement on the interfacial bonding strength, flexural modulus, and other mechanical properties of the resultant wood fiber/high‐density polyethylene (HDPE) composites was mainly related to the coupling agent type, function groups, molecular weight, concentration, and chain structure. As a coupling agent, maleated polyethylene (MAPE) had a better performance in WPC than oxidized polyethylene (OPE) and pure polyethylene (PPE) because of its stronger interfacial bonding. A combination of the acid number, molecular weight, and concentration of coupling agents had a significant effect on the interfacial bonding in WPC. The coupling agents with a high molecular weight, moderate acid number, and low concentration level were preferred to improve interfacial adhesion in WPC. The backbone structure of coupling agents also affected the interfacial bonding strength. Compared with the untreated composites, modified composites improved the interfacial bonding strength by 140% on maximum and the flexural storage modulus by 29%. According to the statistical analysis, 226D and 100D were the best of the seven coupling agents. The coupling agent performance was illustrated with the brush, switch, and amorphous structures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 93–102, 2005     

Effect of Coupling Agent Concentration,Fiber Content,and Size on Mechanical Properties of Wood/HDPE Composites

In this study, the influence of coupling agent concentration (0 and 3 wt%), wood fiber content (50, 60, 70, and 80 wt%), and size (40–60, 80–100, and 160–180 mesh) on the mechanical properties of wood/high-density-polyethylene (HDPE) composites (WPCs) was investigated. WPC samples were prepared with poplar wood-flour, HDPE, and polyethylene maleic anhydride copolymer (MAPE) as coupling agent. It was found that the tensile properties and the flexural properties of the composites were improved by the addition of 3 wt% MAPE, and the improved interfacial adhesion was well confirmed by SEM micrographs. It was also observed that the best mechanical properties of wood/HDPE composites can be reached with larger particle size in the range studied, while too-small particle size was adverse for the mechanical properties of wood/HDPE composites. Moreover, the tensile modulus, tensile strength, and flexural strength of WPCs decreased with the increase in fiber content from 50 to 80 wt%; the flexural modulus of WPCs increased with the increase in fiber content from 50 to 70 wt% and then decreased as the fiber content reached 80 wt%. The variances in property performance are helpful for the end-user to choose an appropriate coupling agent (MAPE) concentration, wood fiber content, and particle size based on performance needs and cost considerations.     

Effects of repetitive processing,wood content,and coupling agent on the mechanical,thermal, and water absorption properties of wood/polypropylene green composites

In an effort to determine to what extent natural fiber/plastic composites were recyclable, this study conducted repetitive processing cycles on wood flour/polypropylene composites through extrusion up to three times followed by injection molding. Mechanical properties of the composites, containing 10–50?wt% wood flour and with/without addition of 3?wt% maleic anhydride polypropylene (MAPP) as coupling agent, were evaluated by conducting tensile test, thermal analysis, and water absorption test. Repetitive processing as well as wood content and coupling agent addition influenced physical properties of the composites. MAPP functioned well in improving fiber-matrix adhesion in terms of mechanical properties. Repetitive processing did not deteriorate the composite’s properties; rather opposite effect was shown. Thermal analysis indicated that the alteration in properties was contributed by the molecular condition of the polypropylene matrix. Water absorption increased with the wood flour content but reduced when MAPP was added and with more processing cycles.     

Durability of wood flour‐plastic composites exposed to accelerated freeze–thaw cycling. Part I. Rigid PVC matrix

This study examined the effects of accelerated freeze–thaw actions on the durability of wood fiber‐plastic composites. Rigid PVC formulations filled with various concentrations of wood flour (both pine and maple) were processed in a counterrotating twin‐screw extruder and exposed to cyclic freeze–thaw actions according to ASTM Standard D6662. Freeze–thaw cycling was also modified by omitting portions of the test (either the water or freezing) to verify whether or not moisture was the primary cause for property loss. The durability of exposed samples was assessed in terms of flexural properties, density, and dimensional stability. Scanning electron micrographs of unexposed and freeze–thaw‐exposed samples were taken to qualitatively evaluate the interfacial adhesion between the wood flour and PVC matrix. The experimental results indicated that the density was not affected by freeze–thaw cycling. The dimensional stability was also relatively unaffected, although greater wood flour content exhibited greater dimensional change. The loss in stiffness of the composites was statistically significant after only two freeze–thaw cycles, regardless of both the wood species and content. Conversely, the strength of the composites was not significantly affected by five freeze–thaw cycles at lower wood flour contents (50 and 75 phr). The deleterious effects of the freeze–thaw actions on the strength of the composites became apparent at higher wood flour content (100 phr) after only two freeze–thaw cycles for maple flour and five freeze–thaw cycles for pine flour. The property loss was attributed primarily to the water portion of the cycling, which appears to have led to the decreased interfacial adhesion between the wood flour and the rigid PVC matrix. J. VINYL. ADDIT. TECHNOL. 11:1–8, 2005. © 2005 Society of Plastics Engineers.     

Mechanical,flammability, and thermal properties of polyvinyl chloride‐wood composites with carbide slag

Carbide slag, an industrial waste produced by calcium carbide hydrolysis to prepare C₂H₂ gas, was successfully used as inorganic filler in the production of polyvinyl chloride (PVC)‐wood composites. carbide slag had an average diameter of 8.1 μm which thermally decomposed at about 450°C, and its main component was Ca(OH)₂. Incorporating carbide slag into PVC‐wood composites substantially decreased the flexural, tensile, and impact strength of the composites as a result of the poor interfacial adhesion between carbide slag and PVC matrix, which could be evidently observed from the scanning electron microscopy (SEM) study. To give carbide slag better use, silane coupling agent KH570 were chose to modify carbide slag. The results indicated that adding carbide slag modified by KH570 (MCS) into PVC‐wood composites could significantly improve its notched impact strength and flexural modulus. The thermogravimetric analysis (TGA) data showed that with the addition of MCS, composite had better thermal stability. It also turned out that with the addition of MCS, its smoke suppression property and flammability were enhanced effectively. To ensure sufficient properties of PVC‐wood composites, the optimal adding content of MCS was 20 phr and it leaded to remarkable performance (its flexural modulus was 3.4 GPa, notched impact strength was 3.87 KJ/m², limiting oxygen index value was 41.5% and smoke density ranting was 55.1%), all of which endowed PVC‐wood composites better utilization. All the results indicated that the preparation of PVC‐wood composites with carbide slag could resolve environmental pollution, reuse carbide slag in different fields, and provide a new method for resource utilization of carbide slag. POLYM. COMPOS., 38:2898–2906, 2017. © 2015 Society of Plastics Engineers     

Wood/plastic composites co‐extruded with multi‐walled carbon nanotube‐filled rigid poly(vinyl chloride) cap layer

Wood/plastic composites (WPCs) can absorb moisture in a humid environment due to the hydrophilic nature of the wood in the composites, making products susceptible to microbial growth and loss of mechanical properties. Co‐extruding a poly(vinyl chloride) (PVC)‐rich cap layer on a WPC significantly reduces the moisture uptake rate, increases the flexural strength but, most importantly, decreases the flexural modulus compared to uncapped WPCs. A two‐level factorial design was used to develop regression models evaluating the statistical effects of material compositions and a processing condition on the flexural properties of co‐extruded rigid PVC/wood flour composites with the ultimate goal of producing co‐extruded composites with better flexural properties than uncapped WPCs. Material composition variables included wood flour content in the core layer and carbon nanotube (CNT) content in the cap layer of the co‐extruded composites, with the processing temperature profile for the core layer as the only processing condition variable. Fusion tests were carried out to understand the effects of the material compositions and processing condition on the flexural properties. Regression models indicated all main effects and two powerful interaction effects (processing temperature/wood flour content and wood flour content/CNT content interactions) as statistically significant. Factors leading to a fast fusion of the PVC/wood flour composites in the core layer, i.e. low wood flour content and high processing temperature, were effective material composition and processing condition parameters for improving the flexural properties of co‐extruded composites. Reinforcing the cap layer with CNTs also produced a significant improvement in the flexural properties of the co‐extruded composites, insensitive to the core layer composition and the processing temperature condition. Copyright © 2009 Society of Chemical Industry     

Investigation of the dynamic mechanical behavior of polypropylene/(wood flour)/(kenaf fiber) hybrid composites

Polypropylene/(wood flour)/(kenaf fiber) hybrid composites were prepared in an internal mixer. Kenaf was considered as a fibrous filler and wood flour as a particulate filler. The lignocellulosic loading used was 50%. Dynamic mechanical thermal analysis properties such as storage modulus (E′), loss modulus (E″), damping factor (tan δ), and adhesion factor were evaluated. It was found that the adhesion factor could interpret the interfacial adhesion between lignocellulosic fillers and the plastic matrix macroscopically. This factor was affected by the type of filler used and the coupling agent concentration. The variation of storage modulus was affected more by the shape of the filler and the coupling agent concentration at higher temperatures than at temperatures below the glass transition. Owing to a higher probability of agglomeration in a sample containing 50 wt% of wood flour, the storage modulus and complex viscosity of this sample were higher than those of other samples. Cole‐Cole diagrams showed that the homogeneity of samples containing a higher amount of coupling agent was higher than that of samples with a lower concentration. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Comparative mechanical,fire‐retarding,and morphological properties of high‐density polyethylene/(wood flour) composites with different flame retardants

Aluminum hydroxide, magnesium hydroxide, and 1,2‐bis(pentabromophenyl) ethane were incorporated into high‐density polyethylene (HDPE) and wood flour composites, and their mechanical properties, morphology, and fire‐retardancy performance were characterized. The addition of flame retardants slightly reduced the modulus of elasticity and modulus of rupture of composites. Morphology characterization showed reduced interfacial adhesion among wood flour, HDPE, and flame retardants in the composites compared with control composites (HDPE and wood flour composites without the addition of flame retardants). The flame retardancy of composites was improved with the addition of the flame retardants, magnesium hydroxide and 1,2‐bis(pentabromophenyl) ethane, especially 1,2‐bis(pentabromophenyl) ethane, with a significant decrease in the heat release rate and total heat release. Char residue composition and morphology, analyzed by attenuated total reflectance, Fourier‐transform infrared spectroscopy, and scanning electron microscopy, showed that the char layer was formed on the composite surface with the addition of flame retardants, which promoted the fire performance of composites. The composites with 10 wt% 1,2‐bis(pentabromophenyl) ethane had good fire performance with a continuous and compact char layer on the composite surface. J. VINYL ADDIT. TECHNOL., 24:3–12, 2018. © 2015 Society of Plastics Engineers     

Flame retardancy,antifungal efficacies,and physical–mechanical properties for wood/polymer composites containing zinc borate

This work aimed to examine flame retardancy, antifungal performance and physical–mechanical properties for silane‐treated wood–polymer composites (WPCs) containing zinc borate (ZnB). ZnB with content from 0.0 to 7.0 wt% was added to WPCs, and silane‐treated wood contents were varied. The polymers used were poly(vinyl chloride) (PVC) and high‐density polyethylene (HDPE). The decay test was performed according to the European standard EN 113. Loweporus sp., a white‐rot fungus, was used for antifungal performance evaluation. Antifungal performance was observed to decrease with wood content. Incorporation of ZnB at 1.0 wt% significantly increased the antifungal performance of WPCs. ZnB content of greater than 1.0 wt% lowered the antifungal properties of WPCs. The results suggested that the wood/PVC composite exhibited better antifungal performance than the wood/HDPE composite. The addition of wood flour to PVC and HDPE decreased flame retardancy, whereas the incorporation of ZnB retained the flame retardancy. ZnB was found to be more appropriate for wood/PVC than wood/HDPE as a result of hydrogen chloride generated from the dehydrochlorination reaction of PVC. The results indicated that the addition of ZnB did not affect the physical‐mechanical properties of neat polymers and the composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Foaming of rigid PVC/wood‐flour composites through a continuous extrusion process

The effects of chemical foaming agent (CFA) types (endothermic versus exothermic) and concentrations as well as the influence of all‐acrylic processing aid on the density and cell morphology of extrusion‐foamed neat rigid PVC and rigid PVC/wood‐flour composites were studied. Regardless of the CFA type, the density reduction of foamed rigid PVC/wood‐flour composites was not influenced by the CFA content. The cell size, however, was affected by the CFA type, independent of CFA content. Exothermic foaming agent produced foamed samples with smaller average cell sizes compared to those of endothermic counterparts. The experimental results indicate that the addition of an all‐acrylic processing aid in the formulation of rigid PVC/wood‐flour composite foams provides not only the ability to achieve density comparable to that achieved in the neat rigid PVC foams, but also the potential of producing rigid PVC/wood‐flour composite foams without using any chemical foaming agents.     

Waste pine cones as a source of reinforcing fillers for thermoplastic composites

In this study, we evaluated some physical and mechanical properties of polypropylene (PP) composites reinforced with pine‐cone flour and wood flour. Five types of wood–plastic composites (WPCs) were prepared from mixtures of cone flour, wood flour, PP, and a coupling agent. The water resistance and flexural properties of the composites were negatively affected by an increase in cone‐flour content. Extractives in the cone flour had a significant effect on the flexural properties of the WPCs. However, the flexural properties and water resistance of the WPC samples were not significantly affected by the addition of 10 wt % of the cone flour when compared to the WPC samples made from wood flour. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Reinforcement of rigid PVC/wood‐flour composites with multi‐walled carbon nanotubes

Multi‐walled carbon nanotubes (CNT) were compounded with PVC by a melt blending process based on fusion behaviors of PVC. The effects of CNT content on the flexural and tensile properies of the PVC/CNT composites were evaluated in order to optimize the CNT content. The optimized CNT‐reinforced PVC was used as a matrix in the manufacture of wood‐plastic composites. Flexural, electrical, and thermal properties of the PVC/wood‐flour composites were evaluated as a function of matrix type (nonreinforced vs. CNT‐reinforced). The experimental results indicated that rigid PVC/wood‐flour composites with properties similar to those of solid wood can be made by using CNT‐reinforced PVC as a matrix. The CNT‐reinforced PVC did not influence the electrical and thermal conductivity of the PVC/wood‐flour composites. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers.     

Manufacture of rigid PVC/wood‐flour composite foams using moisture contained in wood as foaming agent

Relatioships between the density of foamed rigid PVC/wood‐flour composites and the moisture content of the wood flour, the chemical foaming agent (CFA) content, the content of all‐acrylic foam modifier, and the extruder die temperature were determined by using a response surface model based on a four‐factor central composite design. The experimental results indicated that there is no synergistic effect between teh CFA content and the moisture content of the wood flour. Wood flour moisture could be used effectively as foaming agent in the production of rigid PVC/wood‐flour composite foams. Foam density as low as 0.4 g/cm³ was produced without the use of chemical foaming agents. However, successful foaming of rigid PVC/wood‐flour composite with moisture contained in wood flour strongly depends upon the presence of all‐acrylic foam modifier in the formulation and the extrusion die temperature. The lowest densities were achieved when the all‐acrylic foam modifier concentration was between 7 phr and 10 phr and extruder die temperature was as low as 170°C.     

Mechanical and thermal properties of wood‐plastic composites reinforced with hexagonal boron nitride

Mechanical, thermal, and morphological properties of injection molded wood‐plastic composites (WPCs) prepared from poplar wood flour (50 wt%), thermoplastics (high density polyethlyne or polypropylene) with coupling agent (3 wt%), and hexagonal boron nitride (h‐BN) (2, 4, or 6 wt%) nanopowder were investigated. The flexural and tensile properties of WPCs significantly improved with increasing content of the h‐BN. Unlike the tensile and flexural properties, the notched izod impact strength of WPCs decreased with increasing content of h‐BN but it was higher than that of WPCs without the h‐BN. The WPCs containing h‐BN were stiffer than those without h‐BN. The tensile elongation at break values of WPCs increased with the addition of h‐BN. The differential scanning calorimetry (DSC) analysis showed that the crystallinity, melting enthalpy, and crystallization enthalpy of the WPCs increased with increasing content of the h‐BN. The increase in the crystallization peak temperature of WPCs indicated that h‐BN was the efficient nucleating agent for the thermoplastic composites to increase the crystallization rate. POLYM. COMPOS., 35:194–200, 2014. © 2013 Society of Plastics Engineers     

Mica reinforced nylon‐6: Effect of coupling agents on mechanical,thermal, and dielectric properties

The effects of applying titanate (TYZOR® TPT) and silane (DYNASYLAN VTMO) coupling agents to wet ground muscovite mica in nylon‐6 composites are described. Nylon‐6 composites of 5–40 wt % filler loadings were compounded using an APV Baker twin‐screw extruder. Mica (25 wt %) brought about an increase in the Young's modulus, flexural strength, and flexural modulus but did not produce significant variations in tensile and impact strength. Hence different coupling agents were employed. It was observed that titanate coupling agent improved the tensile strength and the Young's modulus of the composites much while the impact properties were enhanced by the silane coupling agent. An attempt was made to use ?‐caprolactum in improving the interfacial adhesion of the filler and the matrix. It was observed that ?‐caprolactum improved the flexural modulus of the composites most. The effect of coupling agents on the dielectric strength, heat distortion temperature, and morphology were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4074–4081, 2006     

Foam extrusion of high density polyethylene/wood‐flour composites using chemical foaming agents

A one‐way analysis of variance and thermal analysis were performed in this study to examine the influences of the contents, types (exothermic vs. endothermic), and forms (pure vs. masterbatch) of chemical foaming agents (CFAs), as well as the use of coupling agents, on the density reduction (or void fraction) and cell morphology of extrusion‐foamed neat high density polyethylene (HDPE) and HDPE/wood‐flour composites. The CFA types and forms did not affect the void fractions of both the neat HDPE and HDPE/wood‐flour composites. However, a gas containment limit was observed for neat HDPE foams whereas the average cell size achieved in the HDPE/wood‐flour composite foams remained insensitive to the CFA contents, irrespective of the foaming agent types. The experimental results indicated that the use of coupling agent in the formulation was required to achieve HDPE/wood‐flour composite foams with high void fraction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3139–3150, 2003