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.     

Novel coupling agents for PVC/wood‐flour composites *

Effective interfacial adhesion between wood fibers and plastics is crucial for both the processing and ultimate performance of wood–plastic composites. Coupling agents are added to wood–plastic composites to promote adhesion between the hydrophilic wood surface and hydrophobic polymer matrix, but to date no coupling agent has been reported for PVC/wood‐fiber composites that significantly improved their performance and was also cost‐effective. This article presents the results of a study using chitin and chitosan, two natural polymers, as novel coupling agents for PVC/wood‐flour composites. Addition of chitin and chitosan coupling agents to PVC/wood‐flour composites increased their flexural strength by ～20%, their flexural modulus by ～16%, and their storage modulus by ～33–74% compared to PVC/wood‐flour composite without the coupling agent. Significant improvement in composite performance was attained with 0.5 wt% of chitosan and when 6.67 wt% of chitin was used. J. VINYL ADDIT. TECHNOL., 11:160–165, 2005. © 2005 Society of Plastics Engineers     

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.     

Mechanical properties of extrusion‐foamed rigid PVC/wood‐flour composites

This study was conducted to characterize the mechanical properties of extrusion‐foamed neat rigid PVC and rigid PVC/wood‐flour composites by using endothermic and exothermic chemical foaming agents (CFAs). The specific elongation at break (ductility) of the samples was improved by foaming, while the opposite trend was observed for the tensile strength and modulus of the samples, regardless of the chemical foaming agent type. In addition, experimental results indicated that foaming reduced the Izod impact resistance of both neat rigid PVC and rigid PVC/wood‐flour composites but that this reduction was not statistically significant for the composites. A comparison between batch microcellular processing and extrusion foam processing was made, which demonstrated that foams with very fine cells (microcellular processed) exhibit better impact strength than foams with larger cells (extrusion processed with CFAs).     

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     

Morphology and mechanical properties of PVC/straw‐fiber coated with liquid nitrile‐butadiene rubber composites

This study exhibited an approach of high‐value utilization of straw fiber (SF) in polymer composites. The rigid poly(vinyl chloride) [PVC]/SF and PVC/SF coated with liquid nitrile‐butadiene rubber (PVC/LNBR‐SF) composites were both fabricated by melt mixing. The chemical structure and crystal structure of LNBR‐SF were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and X‐ray diffraction (XRD). The mechanical properties and micro‐structure of PVC/SF and PVC/LNBR‐SF composites were also studied. FTIR and XRD results showed that the chemical structure and crystal structure of SF did not change after modifying with LNBR. The mechanical properties analysis showed that the PVC/LNBR‐SF composites exhibited better tensile strength, elongation at break and notched impact strength than those of PVC/SF composites owing to the compatibilization and toughening effect of LNBR. Scanning electron microscope results indicated that the LNBR improved the dispersion of SF in PVC matrix to some extent. The interface adhesion between SF and PVC matrix with adding LNBR was also enhanced. These results suggested that PVC/LNBR‐SF composites exhibited promising potential for practical application in substitute for wood. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44119.     

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     

Online measurement of rheological properties of PVC/wood‐flour composites

By using a factorial design approach, this study examined the effect of the component materials on the viscoelastic properties of PVC/wood‐flour composites. Statistical analysis was performed to determine the effects of wood‐flour content, acrylic modifier content, and plasticizer content on the die swell ratio and viscosity of the composites measured online on a conical twin‐screw extrusion capillary rheometer. The viscoelastic properties of the samples also were measured using dynamic mechanical analyzer (DMA). Wood‐flour content and acrylic modifier content were the two important variables affecting the die swell ratio, whereas the addition of a low level of plasticizer did not affect this ratio. The die swell increased with the increased acrylic modifier content, but it was reduced considerably by adding wood flour into the PVC matrix. The true viscosity of neat PVC and PVC/wood‐flour composites decreased with the plasticizer content, irrespective of the acrylic modifier content. However, the addition of acrylic modifier significantly increased the viscosity of unfilled PVC, while an opposite trend was observed for the composites, owing to the differing effect of acrylic modifier on the melt elasticity and viscosity of these materials. J. Vinyl Addit. Technol. 10:121–128, 2004. © 2004 Society of Plastics Engineers.     

Mold susceptibility of rigid PVC/wood‐flour composites

Rigid PVC/wood‐flour composite lumber containing either hardwood (maple) or a softwood (southern pine) wood flour at different levels of wood‐flour content was evaluated for susceptibility to fungal colonization and discoloration by using standard tests that mimicked exterior (ASTM G21) and interior (ASTM D3273) environments, respectively. In the exterior test protocol, although both types of PVC/wood‐flour composite lumber exhibited fungal colonization and discoloration, the composites containing maple exhibited greater discoloration than those containing pine. Irrespective of wood species, fungal colonization and discoloration in the composite lumber were greater at the bottom faces where they were in constant contact with moisture. The wood content range (50–100 phr) used in this study showed no effect on extent of fungal colonization and discoloration. All composites showed no discoloration in the interior test protocol. Both optical microscopy and environmental scanning electron microscopy clearly demonstrated that wood flour particulates are not completely encapsulated by the PVC matrix, so that exposed wood flour in the surface crevices of the composite lumber may serve as points of moisture sorption and staging points for fungal colonization and discoloration. J. Vinyl Addit. Technol. 10:179–186, 2004. © 2004 Society of Plastics Engineers.     

PVC/wood‐flour composites compatibilized with chlorinated polyethylene

Chlorinated polyethylene has been demonstrated to be an effective compatibilizer for dissimilar materials in various mixed‐polymer or recycled‐polymer systems. In this paper the use of chlorinated polyethylene to compatibilize polymer/natural‐fiber composites is discussed. Examples of applications in PVC/wood‐flour composites are given.     

Investigating the acoustical properties of carbon fiber‐, glass fiber‐, and hemp fiber‐reinforced polyester composites

Wood is one of the main materials used for making musical instruments due to its outstanding acoustical properties. Despite such unique properties, its inferior mechanical properties, moisture sensitivity, and time‐ and cost‐consuming procedure for making instruments in comparison with other materials (e.g., composites) are always considered as its disadvantages in making musical instruments. In this study, the acoustic parameters of three different polyester composites separately reinforced by carbon fiber, glass fiber, and hemp fiber are investigated and are also compared with those obtained for three different types of wood specimens called poplar, walnut, and beech wood, which have been extensively used in making Iranian traditional musical instruments. The acoustical properties such as acoustic coefficient, sound quality factor, and acoustic conversion factor were examined using some non‐destructive tests based on longitudinal and flexural free vibration and also forced vibration methods. Furthermore, the water absorption of these polymeric composites was compared with that of the wood samples. The results reveal that the glass fiber‐reinforced composites could be used as a suitable alternative for some types of wood in musical applications while the carbon fiber‐reinforced composites are high performance materials to be substituted with wood in making musical instruments showing exceptional acoustical properties. POLYM. COMPOS., 35:2103–2111, 2014. © 2014 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.     

Effects of impact modifiers on the properties of rigid PVC/wood‐fiber composites

This study examined the effects of impact modifier types and addition levels on the mechanical properties of rigid PVC/wood‐fiber composites. The impact resistance of rigid PVC/wood‐fiber composites depends strongly on the type and content of impact modifier. With the proper choice of modifier type and concentration, the impact strength of rigid PVC/wood‐fiber composites can be significantly improved without degrading the tensile properties. Methacrylate‐butadiene‐styrene and all‐acrylic modifiers performed in a similar manner and were more effective and efficient in improving the impact resistance of rigid PVC/wood‐fiber composites than the chlorinated polyethylene modifier.     

Mechanical,thermal, and water uptake characteristics of woodflour‐filled polyvinyl chloride/acrylonitrile butadiene styrene blends

Woodflour‐filled composites based on polymeric blends of polyvinyl chloride (PVC) and super high‐impact grade ABS were developed. Mechanical, thermal, and water uptake characteristics of the PVC/ABS matrix and their wood composites were evaluated. In the case of PVC/ABS matrix, the blend at a mass ratio of 50/50 rendered the impact strength with a very high value of up to 65 kJ/m², noticeably higher than those of the parent resins, that is, 6 kJ/m² of PVC and 35 kJ/m² of ABS. Dynamic mechanical analysis thermograms showed two distinct glass transition temperatures (T_gs) that shifted toward each other indicating partial miscibility of the blends. Water absorption of the blends after 24 h immersion was low, that is, within the range of 0.04–0.2 wt % and exhibits a behavior closed to pseudo‐Fickian type. The obtained PVC/ABS wood composites exhibited an increase of flexural modulus as well as T_gs with an increase of woodflour content. Finally, impact strength of the PVC/ABS composites was significantly higher than those of PVC composites or polyethylene composites comparing at the same woodflour content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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,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‐fiber‐reinforced poly(lactic acid) composites: Evaluation of the physicomechanical and morphological properties

This article presents the results of a study of the processing and physicomechanical properties of environmentally friendly wood‐fiber‐reinforced poly(lactic acid) composites that were produced with a microcompounding molding system. Wood‐fiber‐reinforced polypropylene composites were also processed under similar conditions and were compared to wood‐fiber‐reinforced poly(lactic acid) composites. The mechanical, thermomechanical, and morphological properties of these composites were studied. In terms of the mechanical properties, the wood‐fiber‐reinforced poly(lactic acid) composites were comparable to conventional polypropylene‐based thermoplastic composites. The mechanical properties of the wood‐fiber‐reinforced poly(lactic acid) composites were significantly higher than those of the virgin resin. The flexural modulus (8.9 GPa) of the wood‐fiber‐reinforced poly(lactic acid) composite (30 wt % fiber) was comparable to that of traditional (i.e., wood‐fiber‐reinforced polypropylene) composites (3.4 GPa). The incorporation of the wood fibers into poly(lactic acid) resulted in a considerable increase in the storage modulus (stiffness) of the resin. The addition of the maleated polypropylene coupling agent improved the mechanical properties of the composites. Microstructure studies using scanning electron microscopy indicated significant interfacial bonding between the matrix and the wood fibers. The specific performance evidenced by the wood‐fiber‐reinforced poly(lactic acid) composites may hint at potential applications in, for example, the automotive and packaging industries. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4856–4869, 2006     

Antifungal properties and material characteristics of PVC and wood/PVC composites doped with carbamate‐based fungicides

Antifungal properties of polyvinylchloride (PVC) and wood/PVC composites (WPVC) were studied with two different fungicides through disk diffusion and dry weight techniques against Aspergillus niger as a testing fungus. Three different types of woods, including Xylia kerrii Craib & Hutch.(XK), Hevea brasiliensis Muell.(HB), and Mangifera indica Linn.(MI), were used. The disk diffusion results revealed that the addition of 3‐iodopropinyl‐N‐butylcarbamate (IPBC) in the PVC and WPVC markedly reduced the diameter of fungi, whereas the addition of methylbenzimidazole‐2‐ylcarbamate(Carbendazim) did not. The results from IPBC samples by the dry weight technique corresponded to those by the disk diffusion method. Adding fungicides tended to slightly increase the flexural properties of PVC, whereas in the case of WPVC those properties were deteriorated by IPBC and carbendazim additions. The total color change was less when IPBC only was introduced into PVC. FTIR spectra suggested that no chemical structure changes were observed after the addition of IPBC and carbendazim. The higher surface contact angle and fungicide release values for IPBC samples could imply greater diffusibility of IPBC in PVC and WPVC matrices, accompanied by increased antifungal activity. WPVC with HB wood showed the best antifungal performance, at an optimal concentration of 10,000 ppm, when compared with XK and MI woods. POLYM. ENG. SCI., 54:1248–1259, 2014. © 2013 Society of Plastics Engineers     

Recycling of polypropylene‐based eco‐composites

BACKGROUND: Renewable resources and recyclable thermoplastic polymers provide an attractive eco‐friendly quality as well as environmental sustainability to the resulting natural fibre‐reinforced composites. The properties of polypropylene (PP)‐based composites reinforced with rice hulls or kenaf fibres were investigated with respect to their recyclability. Rice hulls from rice processing plants and natural lignocellulosic kenaf fibres from the bast of the plant Hibiscus cannabinus represent renewable sources that could be utilized for composites. Maleic anhydride‐grafted PP was used as a coupling agent to improve the interfacial adhesion between fillers and matrix. Composites containing 30 wt% reinforcement were manufactured by melt mixing and their mechanical and thermal properties were determined. The composites were then pelletized and reprocessed by melt mixing. Finally, structure/properties relationships were investigated as a function of the number of reprocessing cycles. RESULTS: It is found that the recycling processes do not induce very significant changes in flexural strength and thermal stability of the composites. In particular PP‐based composites reinforced with kenaf fibres are less sensitive to reprocessing cycles with respect to PP‐based composites reinforced with rice hulls. CONCLUSION: The response of PP‐based composites reinforced with rice hulls or kenaf fibres is promising since their properties remain almost unchanged after recycling processes. Moreover, the recycled composites are suitable for applications as construction materials for indoor applications. In fact, the flexural strength and modulus of these materials are comparable to those of conventional formaldehyde wood medium‐density fibreboards. Copyright © 2008 Society of Chemical Industry     

Enhanced toughness of multilayer graphene‐filled poly(VInyl chloride) composites prepared using melt‐mixing method

In order to improve toughness of rigid poly(vinyl chloride) (PVC), we prepared multilayer graphene (MLG) filled PVC composites through conventional melt‐mixing methods by taking advantages of easy dispersion and high flexibility of graphene. Microstructure, static, and dynamic mechanical properties of the MLG/PVC composites were investigated in details. We found that a small amount of MLG loadings (0.36 wt%) could greatly increase tensile fracture toughness and impact strength of the MLG/PVC composites, which is mainly attributed to high flexibility of the crumpled MLG throughout PVC matrix. Moreover, the presence of MLG can weaken intermolecular interactions and improve segmental motion of PVC chains, consequently resulting in low glass transition temperature and high toughness of the MLG/PVC composites. By virtue of its enhanced toughness and easy operation, the MLG/PVC composites show great potential to be used as high‐performance composites in many fields. POLYM. COMPOS., 38:138–146, 2017. © 2015 Society of Plastics Engineers