Effects of UV weathering and a CeO2‐based coating layer on the mechanical and structural changes of wood/PVC composites

Composite samples (WPVCs) of poly(vinyl chloride) (PVC) and wood flour were prepared in the PVC:wood weight ratio of 1:1, and the mechanical and structural changes of the composites were assessed in terms of UV aging time and condensation temperature. Acrylic coating containing cerium dioxide as a UV absorber was used for moderation of the mechanical and structural changes of PVC in the WPVC composites. The experimental results indicated that the tensile and flexural properties of the composites monotonically decreased when the aging time was increased, the effect being more pronounced at high condensation temperatures. It was observed that the polyene and yellowness indexes of the WPVC composites increased with UV aging time. The hydrophilicity of the WPVC was quantified by contact angle results and found to increase with increasing UV aging because of hydrogen bonding between ? OH groups on the wood surfaces and water molecules. The acrylic coating containing CeO₂ proposed in this work was sufficiently effective for maintaining the levels of hydrophilicity and mechanical properties of the WPVC composites. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

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     

Mechanical and morphological properties for sandwich composites of wood/PVC and glass fiber/PVC layers

This work manufactured sandwich composites from glass fiber/poly(vinyl chloride) (GF/PVC) and wood/PVC layers, and their mechanical and morphological properties of the composites in three GF orientation angles were assessed. The effects of K value (or viscosity index) of PVC and Dioctyl phthalate (DOP) loading were of our interests. The GF/PVC was used as core layer whereas wood/PVC was the cover layers. The experimental results indicated that PVC with low K value was recommended for the GF/PVC core layer for fabrication of GF/WPVC sandwich composites. The improvement of PVC diffusion at the interface between the GF and the PVC core layer was obtained when using PVC with K value of 58. This was because it could prevent de‐lamination between composite layers which would lead to higher mechanical properties of the sandwich composites, except for the tensile modulus. The sandwich composites with 0° GF orientation possessed relatively much higher mechanical properties as compared with those with 45° and 90° GF orientations, especially for the impact strength. Low mechanical properties of the sandwich composites with 45° and 90° GF orientation angles could be overcome by incorporation of DOP plasticizer into the GF/PVC core layer with the recommended DOP loadings of 5–10 parts per hundred by weight of PVC components. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of cross‐section design and loading direction on the creep and fatigue properties of wood/PVC composite beams

The creep and fatigue properties of two wood/poly(vinyl chloride) (WPVC) composite beams were studied under flexural and cyclic deformations. The effects of cross‐section design and load direction were the main interests. The weight ratio of the wood and PVC compound used was 1:1, and the composites were produced by using an industrial‐scale twin‐screw extruder. In creep testing, the changes in WPVC beam displacement for the edgewise and flatwise directions increased with time. The WPVC composite with a greater size (thickness) and number of cores had the higher creep resistance. Testing a WPVC composite in the flatwise direction gave less time‐dependence than testing in the edgewise direction. The recommended applied loads for optimum creep resistance of the WPVC specimens were found to be 20 and 30% of the ultimate load to failure, depending on the size and number of cores for the cross‐section used. In fatigue testing, the number of cycles to failure for both WPVC composite specimens tested in the flatwise direction was greater than that for testing in the edgewise direction. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Effects of acrylic‐based processing aids on processibility,rheology, thermal and structural stability,and mechanical properties of PVC/wood–sawdust composites

Methyl methacrylate and ethylacrylate (MMA‐co‐EA) and methyl methacrylate and butylacrylate (MMA‐co‐BA) copolymeric processing aids were introduced into poly(vinyl chloride) (PVC)/33.3 wt % wood–sawdust composites containing 0.6 and 2.4 phr of calcium stearate lubricant. The properties of the composites were monitored in terms of processibility, rheology, thermal and structural stability, and mechanical properties. It was found that the mixing torque, wall shear stress, and extrudate swell ratio increased with increasing processing aid content because of increased PVC entanglement. MMA‐co‐BA (PA20) was found to be more effective than MMA‐co‐EA (K120 and K130), this being associated with the flexibility of the processing aids, and the dipole–dipole interactions between sawdust particles and polymeric processing aids. The sharkskin characteristic of the composite extrudate at high extrusion rate was moderated by the presence of processing aids. Adding the acrylic‐based processing aids and lubricant into PVC/sawdust composites improved the thermal and structural stability of the composites, which were evidenced by an increase in glass transition and decomposition temperatures and a decrease in polyene sequences, respectively. The changes in the mechanical properties of the composites involved a composite homogeneity, which was varied by degree of entanglement and the presence of wood sawdust, and un‐reacted processing aids left in the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 782–790, 2004     

甘油锌及其复合光稳定剂对PVC的光稳定作用研究

对甘油锌用作PVC光稳定剂的光稳定作用进行了研究,考察了PVC紫外光老化后力学性能和颜色的变化。结果表明,甘油锌对PVC具有明显的光稳定作用,与受阻胺光稳定剂Tinuvin770复配,具有明显的正协同效应,当二者的质量配比达到2∶3 时,对PVC的光稳定效果最佳。     

Photodegradation of some poly(vinyl chloride) (PVC) blends: PVC/ethylene-vinyl acetate (EVA) copolymers and PVC/butadiene-acrylonitrile (NBR) copolymers

Poly(vinyl chloride) (PVC) and its blends with polybutadiene-acrylonitrile (NBR) (containing 21.7 weight-percent acrylonitrile (AN), a heterogeneous two-phase system; and containing 41.6 weight-percent of AN, a homogeneous one-phase system) and with polyethylene-vinyl acetate (EVA) (containing 45 weight-percent of vinyl acetate (VA), a heterogenous two-phase system; and containing 65 weight-percent VA, a homogeneous one-phase system) were UV-irradiated (at 3500 Å UV-light (solar spectrum)). After UV irradiation the kinetics measurements were made of the formation of hydroperoxy (OOH) and carbonyl (CO) groups and the changes of mechanical properties: tensile strength, elongation to break, and impact energy. As a result of the photooxidative degradation of PVC blends, decreases of mechanical properties were observed. The effects are more severe in PVC/NBR blends, which contain unsaturated bonds (polybutadiene segments) than in the case of PVC/EVA. The phase structure plays an evident role on the UV degradation only of PVC/NBR blends. The photostability of PVC blends can be slightly improved by introducing Tinuvin P or Ni-chelates photostabilizers.     

The mechanism for inorganic fillers accelerating and inhibiting the UV irradiation aging behaviors of rigid poly(vinyl chloride)

The UV irradiation aging behaviors of PVC composites with several inorganic fillers were studied through Fourier transform spectroscopy (FTIR), ultraviolet spectroscopy (UV‐Vis), differential scanning calorimeter (DSC), scanning electron microscopy (SEM), and mechanical property test. It was found that incorporation of a small amount of the inorganic fillers such as CaCO₃, talc and SiO₂ could hold up the UV aging behaviors of PVC. Those filler‐filled PVC composites sheets after 20 days UV irradiation maintain lower carbonyl index (CI) and good appearance of surfaces, as compared with the corresponding neat PVC sheets, ascribed to high reflection of those fillers to UV light. While montmorillonite (MMT) and pyrophyllite fillers could accelerate the UV aging behaviors of PVC, which could be concluded from both the sharp increase of the CI and lower T_g due to the chain scission reactions because of their high absorbance of these fillers to UV light in 290–400 nm. In these two PVC composites, UV irradiation caused the deterioration of their mechanical properties and the appearance of rough, cracked and chalked surfaces after 20 days UV irradiation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of wood sawdust content on rheological and structural changes,and thermo‐mechanical properties of PVC/sawdust composites

The use of untreated sawdust as a filler in poly(vinyl chloride) (PVC) was examined—the effects of sawdust content on structural and thermal changes, and rheological and mechanical properties being of main interest. The results revealed that the torque and die entrance pressure drop values during mixing were independent of sawdust particles up to 23.1 wt%. The extrudate swell monotonically decreased up to 33.3 wt% sawdust content. Smooth wood‐like texture with controllable size of the extrudate could be obtained at a sawdust content greater than 33.3 wt%. Tensile, impact, flexural and hardness properties of the PVC/sawdust composites considerably decreased with up to 16.7 wt% sawdust content before leveling off for higher sawdust loadings. The composites having sawdust higher than 16.7 wt% showed a benefit of cost savings. The decreases in the mechanical properties of PVC with sawdust are explained in association with the presence of moisture, interfacial defects between fibre and polymer, and fibre dispersions in the PVC matrix. Thermal degradations of PVC in PVC/sawdust composites were evidenced by a decrease in decomposition temperature and an increase in polyene sequences, which were caused by Cl cleavage due to strong hydrogen bonds of fibre–PVC molecules. The maximum of tanδ transition and the glass transition temperature were found to improve with sawdust content as a result of re‐formation of hydrogen bonds between the macromolecules of the fibre and the polymer. The overall results in this work suggest that the properties of PVC/sawdust composites were strongly influenced by sawdust content up to 16.7 wt%. Beyond this value the effect of sawdust content on the properties was comparatively small. Copyright © 2003 Society of Chemical Industry     

纳米TiO_2含量对PVC/稻壳粉木塑复合材料性能的影响

将纳米TiO_2、稻壳粉、聚氯乙烯(PVC)和稳定剂等按一定比例混合,用挤出成型法制备PVC/稻壳粉木塑复合材料。考察纳米TiO_2添加量对PVC/稻壳粉木塑复合材料性能的影响。实验结果表明,随着纳米TiO_2含量的增加,木塑复合材料的力学性能、防水性能和热稳定性呈现先增加后降低的趋势,但木塑复合材料的表面颜色却随着纳米TiO_2含量的增加而逐渐变浅。当纳米TiO_2含量为1.00份时,木塑复合材料的综合性能最好,与未添加纳米TiO_2的木塑复合材料相比,其拉伸强度、冲击强度和弯曲强度分别提高了40.6%,62.2%和19.7%,8 d的吸水率从2.5%降低为1.6%,表面接触角从78.5°增加到82.1°,800℃时的残炭率从21.1%提高到29.5%。     

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     

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.     

Study on PVC composites containing Eugenia jambolana wood flour

This article describes the properties of composites using unplasticized PVC matrix and wood flour (obtained by crushing the bark of Eugenia jambolana) as filler. Composites were prepared by mixing PVC with varying amounts of wood flour (ranging from 10–40 phr; having particle sizes of 100–150 μm and <50μm) using two‐roll mill followed by compression molding. The effect of wood flour content and its particle size on the properties, i.e., mechanical, dynamic mechanical, and thermal was evaluated. Tensile strength, impact strength, and % elongation at break decreased with increasing amounts of wood flour. Stiffness of the composites (as determined by storage modulus) increased with increasing amounts of the filler. Modulus increased significantly when wood flour having particle size <50 μm was used. Morphological characterization (SEM) showed a uniform distribution of wood flour in the composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Effects of cross section design and testing conditions on the flexural properties of wood/PVC composite beams

Highly filled wood/poly(vinyl chloride) (WPVC) composites were manufactured in five different cross sections by using an industrial‐scale twin‐screw extruder. The flexural properties of such composites were evaluated, with the effects of sample direction, span length, and rate of loading also being taken into account. The experimental results suggested that the cross section design of WPVC composite products had a significant effect on the flexural properties. Better flexural properties were obtained when testing the WPVC composites in an edgewise loading direction. The findings of this work suggested that a low number of hollow cores with thick flanges and webs should be used to obtain a composite with better flexural properties. The WPVC composite with low density was observed to exhibit lower flexural strength, and the rate of loading had a marginal effect on the flexural properties of the composites. The minimum L/d ratios of the WPVC beam to be used for steady flexural properties were 10 in the edgewise direction and 16 in the flatwise direction. J. VINYL ADDIT. TECHNOL, 2010. © 2009 Society of Plastics Engineers     

Preparation and evaluation of some benzophenone terpolymers as photostabilizers for rigid PVC

Some terpolymeric stabilizers based on polymerizable derivatives of 2,4‐dihydroxy‐benzophenone were prepared and evaluated as photostabilizers for rigid poly(vinyl chloride) (PVC). The prepared terpolymers, namely, (methyl methacrylate)/(2‐hydroxyethyl methacrylate)/2‐hydroxy‐4‐methacryloxybenzophenone (MMA/HEMA/HBMA) and (methyl methacrylate)/(2‐hydroxyethyl methacrylate)/2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxypropoxy)benzophenone (MMA/HEMA/PBMA), were characterized, and their structures were confirmed by GPC, thermogravimetric analysis, FTIR, and ultraviolet‐visible (UV–vis) spectroscopy. The results revealed that the stabilizing effect of these terpolymers increased upon increasing the stabilizer concentration and the content of UV absorber units in the terpolymers. Promising results were achieved, and the prepared terpolymers showed higher stabilizing efficiency than the corresponding monomeric UV absorbers of low molecular weight. J. VINYL ADDIT. TECHNOL., 2011.© 2011 Society of Plastics Engineers     

Photoaging and stabilization of rigid PVC/wood‐fiber composites

Ultraviolet (UV) weathering performance of unpigmented and rutile titanium dioxide pigmented rigid polyvinyl chloride (PVC)/wood‐fiber composites has been studied. The composite samples were manufactured by dry‐blending PVC, wood fibers, and other processing additives in a high‐intensity mixer. The dry‐blended compounds were extruded and compression molded into panel samples. The manufactured samples were artificially weathered using laboratory accelerated UV tests. Composite samples were exposed to 340‐nm fluorescent UV lamps and assessed every 200 h, for a total of 1200 h of accelerated weathering. Each assessment consisted of a visual examination of surface roughness or erosion, a contact angle measurement, a FTIR collection, and a color measurement. The experimental results indicated that wood fibers are effective sensitizers and that their incorporation into a rigid PVC matrix has a deleterious effect on the ability of the matrix to resist degradation caused ultraviolet irradiation. The light stability of these composites could be improved quite efficiently with the addition of rutile titanium dioxide photoactive pigment during formulation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1943–1950, 2001     

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.     

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     

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.     

An investigation into the thermal stability of PVC/montmorillonite composites

An effective stabilizing system for poly (vinyl chloride) (PVC)/clay composites was established. Different types of stabilizers, i.e., organotin, calcium/zinc, barium/zinc, and an epoxy costabilizer, were investigated. The combination of the organotin stabilizer and the epoxy costabilizer was the most effective stabilizing system. Different grades of Cloisite nanoclays were investigated. Cloisite Na did not cause premature degradation of PVC. Cloisite 10A strongly accelerated the degradation of PVC because of the presence of excess surfactant, while a PVC/Cloisite 30B system showed much better thermal stability because there was less organic impurity in the Cloisite 30B. Phosphonium‐modified clays were also prepared. They showed better thermal stability than ammonium‐modified clays, but the drying conditions still need to be optimized in order to produce a dispersible clay powder. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers