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     

Stabilizations of molecular structures and mechanical properties of PVC and wood/PVC composites by Tinuvin and TiO2 stabilizers

Three different UV stabilizers, 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐ditertpentylphenol (Tinuvin XT833), 2‐(2H‐benzotriazol‐2‐yl)‐p‐cresol (Tinuvin P), or rutile–titanium dioxide (TiO₂) were incorporated into poly(vinyl chloride) (PVC) and wood/PVC (WPVC) composite, and mechanical and physical properties and photostabilities were monitored. The polyene and carbonyl sequences of PVC increased with UV weathering time and with presence of wood flour. The yellowness index increased because of polyene and carbonyl productions, whereas the brightness increased because of the photobleaching of lignin in wood. The photostabilities of PVC and WPVC could be improved through the use of UV stabilizers. Tinuvin P was recommended in this work as the most effective stabilizer for PVC and WPVC composites. The stabilization effect was interfered by presence of wood particles. The mechanical property changes corresponded well to the structural changes under UV for neat PVC. For WPVC composites, the presence of wood particles played more significant effect on the mechanical properties during UV aging than the UV stabilizer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Influence of interfacial interactions on the properties of PVC/cellulosic fiber composites

The surface properties at the interface between thermoplastic and cellulosic fibers strongly influence the mechanical properties of plastic/cellulosic fiber composites. This paper examines the role of surface acid-base properties of plasticized PVC and cellulosic fibers on the mechanical properties of the composites. The acid-base surface characteristics of cellulosic fibers were modified by treating the fibers with γ-aminopropyltriethoxysilane (A-1100), dichlorodiethylsilane, phthalic anhydride, and maleated polypropylene. The empirical acid (K_A) and base (K_D) characteristics (i.e., electron donor/acceptor abilities) of untreated and treated fibers, as well as plasticized PVC, were determined using inverse gas chromatography (IGC) technique. These parameters were used to yield information on the acid-base pair interactions that were correlated with the tensile and notched Izod impact properties of the composites. Acid-base pair interactions have been found to be a valuable parameter in the design of surface modification strategies intended to optimize the tensile strength of the composites. By tailoring the acid-base characteristics of cellulosic fibers and plasticized PVC, a composite with equal tensile strength and greater modulus than unfilled PVC was developed. However, the acid-base factors did not correlate with tensile modulus, the elongation at break, and the notched Izod impact property of PVC/newsprint fiber composites. Aminosilane has been observed to be a suitable adhesion promoter for PVC/wood composites improving significantly the tensile strength of the composites. Other treatments (dichlorodiethylsilane, phtalic anhydride, and maleated polypropylene) were found to be ineffective, giving similar strength compared to the composites with untreated cellulosic fibers. FTIR spectroscopy results suggested that aminosilane was effective because treated cellulosic fibers can react with PVC to form chemical bonds. The resulting bond between PVC and cellulosic fibers accounts for the effectiveness of aminosilane, when compared with other coupling agents.     

GF及偶联剂改性PVC/稻壳木塑复合材料

采用模压成型的方式、通过实验探索玻璃纤维(GF)含量及偶联剂处理对聚氯乙烯(PVC)/稻壳木塑复合材料的力学特性和耐磨性的影响。实验结果表明:PVC/稻壳木塑复合材料的硬度随GF含量增加呈现先减小后增大的趋势。GF含量在15%以下时,随着GF用量的增大,木塑复合材料的拉伸强度与冲击强度总体上随之变大,超过15%则随GF含量增大而减小。而弯曲强度出现先减后增的趋势,弯曲弹性模量则与之相反。木塑复合材料的耐磨损性在GF含量为15%时最佳,摩擦系数在10%时最大。合适的偶联剂处理能增强木塑复合材料的力学性能和耐磨性。其中γ–氨丙基三乙氧基硅烷(KH550)的增强效果比较好,钛酸酯不能提高PVC/稻壳木塑材料的力学性能和耐磨性。     

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     

加工助剂对PVC木塑复合材料性能的影响

研究了4种新型加工助剂对聚氯乙烯(PVC)木塑复合材料的加工特性和物理力学性能的影响,并利用扫描电子显微镜(SEM)研究复合材料的冲击断面。结果表明,以不饱和芳香族碳氢化合物、脂肪烃树脂为主要组分的加工助剂,能够提高木粉在PVC基体中的分散性,改善木粉与PVC的相容性,从而明显提高PVC木塑材料的力学性能和加工性能;以钙皂和饱和脂肪酸酰胺混合物、脂肪醇和脂肪酸酯的混合物为主要组分的加工助剂,对木粉的分散性和复合材料的加工性能有一定的改善,但其用量较大时对复合材料的力学性能有不利影响。     

Calcium carbonate and wood reinforced hybrid PVC composites

In this article, poly(vinyl chloride) (PVC) sandwich‐structured hybrid composites with amorphous calcium carbonate and wood‐filled cores were obtained by compression molding. It has been determined that wood addition up to a weight ratio of 33% reported to the total filler amount is beneficial in improving both the inter‐filler and filler‐matrix interfacial adhesion, which alongside with the promoting of the amorphous PVC matrix crystallization is responsible for an increase up to 34% in the flexural strength of the composites, compared to unfilled PVC. The hybrid filled composites present up to 35% lower friction coefficients and up to 20% higher Brinell hardness values than the composites filled with calcium carbonate alone. Subsequently, wood addition determines an increase in the oxidation onset temperature for PVC and an increase with up to 20% in the sound and thermal‐insulative properties of the composites, compared to unfilled PVC. The dominating dispersive part of the composites surface energy aids in improving the mass and dimensional stability of the assembly to both water and dilute hydrochloric acid aqueous solutions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46317.     

Co‐injection molding of PVC with other thermoplastics: Processing,properties, and applications

Rigid poly(vinyl chloride) (PVC) was co‐injected with glass‐fiber‐reinforced PVC (GFR‐PVC), polypropylene (PP), acrylonitrile‐butadiene‐styrene copolymer (ABS), and polycarbonate (PC) by using the Mono‐sandwich co‐injection process. Up to three through‐thickness skin‐core morphologies were observed along the length of the sample. Near the gate, the core was always a single, continuous layer. In some cases, the core diverged into multiple or discontinuous layers. Farther from the gate, flow of the core ceased, leaving a skin‐only region. The skin and core layers were more uniformly distributed through the test plaque when injection speed was low. Adhesion between PVC and PP was poor. Skin and core layers delaminated, and mechanical properties were poor. The PVC adhered well to GFR‐PVC, ABS, and PC. No layer delamination occurred, and mechanical properties were intermediate between those of the skin and core components alone. Dropped dart impact energy was controlled more by the skin layer than the core. In rigid PVC/GFR‐PVC co‐injected samples, impact energy was 2.5 times greater when GFR‐PVC was the core than when GFR‐PVC was the skin.     

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     

Characterization of PVC cable insulation materials and products obtained after removal of additives

Organic solvents cyclohexane, dichloromethane, hexane, and tetrahydrofuran were tested to separate the dioctylphthalate (DOP) as plasticizer from the poly(vinyl chloride) (PVC)‐based materials. It was found that the efficiency of ultrasound‐enhanced hexane extraction of the DOP from PVC is 70% and the efficiency of the separation of the DOP and other compounds from the PVC by dissolution in THF followed by subsequent precipitation was 98–99%. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to characterize the thermal behavior of PVC materials before and after extraction of plasticizers. It was found that during heating in the range 20–800°C the total mass loss measured for the nontreated, extracted, and precipitated PVC samples was 71.6, 66.6, and 97%, respectively. In the temperature range 200–340°C, the release of DOP, HCl, and CO₂ was observed by simultaneous thermogravimetry (TG)/FTIR. The effect of plasticizers on thermal behavior of PVC‐based insulation material was characterized by DSC in the range ?40–140°C. It was found that, concerning the PVC cable insulation material before treatment, the value of the glass transition temperature (T_g) was 1.4°C, whereas for the PVC sample extracted by hexane, the value of T_g was 39.5°C and for the PVC dissolved in THF and subsequently precipitated, the value of T_g was 80.4°C. Moreover, the PVC samples after extraction of plasticizers, fillers, and other agents were tested to characterize their thermal degradation. The TG and FTIR results of chemically nontreated, extracted, and precipitated samples were compared. The release of DOP, HCl, CO₂, and benzene was studied during thermal degradation of the samples by FTIR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 788–795, 2006     

增塑剂DOP在软PVC和PVC/ABS共混物中的应用

研究了增塑剂DOP对聚氯乙烯（商品牌号SG-3，SG-5）及PVC／ABS共混物力学和硬度等性质的影响及其机理。结果表明：由于DOP小分子对高分子链的物理隔离作用，当DOP含量高于30％时，随DOP用量的增加，PVC树脂及PVC／ABS的断裂伸长率明显增大，体系的拉伸强度、撕裂强度和硬度等略微下降。     

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     

Formulation and properties' evaluation of PVC/(dioctyl phthalate)/(epoxidized rubber seed oil) plastigels

Epoxidized rubber seed oil (4.5% oxirane content, ERSO) was prepared by treating the oil with peracetic acid generated in situ by reacting glacial acetic acid with hydrogen peroxide. The thermal behavior of the ERSO was determined by differential scanning calorimetry. The effect of the epoxidized oil on the thermal stability of poly (vinyl chloride) (PVC) plastigels, formulated to contain dioctyl phthalate (DOP) plasticizer and various amounts of the epoxidized oil, was evaluated by using discoloration indices of the polymer samples degraded at 160°C for 30 min and thermogravimetry at a constant heating rate of 10°C/min up to 600°C. The thermal behavior of the ERSO was characterized by endothermic peaks at about 150°C, which were attributed to the formation of network structures via epoxide groups, and at temperatures above 300°C, which were due to the decomposition of the material. Up to 50% of the DOP plasticizer in the PVC plastisol formulation could be substituted by ERSO without a marked deleterious effect on the consistency of the plastigel formed. In the presence of the epoxidized oil, PVC plastigel samples showed a marked reduction in discoloration and the number of conjugated double bonds, as well as high temperatures for the attainment of specific extents of degradation. These results showed that the ERSO retarded/inhibited thermal dehydrochlorination and the formation of long (n > 6) polyene sequences in PVC plastigels. The plasticizer efficiency/permanence of ERSO in PVC/DOP plastigels was evaluated from mechanical properties' measurements, leaching/migration tests, and water vapor permeability studies. The results showed that a large proportion of DOP could be substituted by ERSO in a PVC plastisol formulation without deleterious effects on the properties of the plastigels. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers.     

The effect of ambient moisture and temperature conditions on the mechanical properties of glass fiber/carbon fiber/nylon 6 sandwich hybrid composites consisting of skin‐core morphologies

The concept of skin‐core (SC) morphology was used to make sandwich hybrid composites in which the skin and core were composed of different fibers in the same matrix. The sandwich blends comprising glass skin with carbon core and vice versa were compared with those of the hybrid composite, while the respective carbon (CF) and glass fiber (GF) composites served as points of reference. The composites were compounded and fabricated into injection molded tensile specimens and 3‐mm thick plaques. The effect of ambient temperature and moisture was studied. The fracture mechanical characterization of the various materials was done by using notched compact tension (CT) specimens. Tensile properties were also used to characterize the composites. Morphogical studies based on scanning electron microscopy and light microscopy were used to elucidate fracture characteristics. Deterioration of properties was noticed under hot and humid conditions. Synergism in flexural properties was observed in the CF/GF/PA hybrid composite. The mechanical properties of the CF/GF/PA hybrid are closer to those of CF/PA, suggesting a cost advantage by substituting half of the carbon fibers with glass fibers. Dynamic mechanical analysis results revealed that synergism in T_g is attained by blending or sandwiching glass and carbon fibers. Morphological studies reaffirmed the skin‐core morphology of the composites. POLYM. COMPOS., 26:52–59, 2005. © 2004 Society of Plastics Engineers.     

PVC/RRPU复合材料的制备及性能研究

以四乙烯五胺/二乙二醇(TEPA/DEG)为解交联剂,采用力化学法使废弃的硬质聚氨酯泡沫解交联,得到可再生的聚氨酯粉末(RRPU),利用GPC测试了RRPU分子质量。采用熔融共混法制备了PVC/RRPU复合材料,研究了RRPU的含量、增塑剂含量对PVC/RRPU复合材料力学性能的影响,并利用SEM观察了复合材料断面形态。研究表明:废弃的硬质聚氨酯泡沫解交联为较小分子量的聚合物,且其分子量分布较窄。当RRPU的含量为70%,DOP的含量为复合材料的15%时,PVC/RRPU复合材料具有较好的力学性能,复合材料断面中相界面模糊,两相黏结作用较好。     

表面处理剂对PVC仿木复合材料性能的影响

使用4种不同类型的含高活性反应基团的聚氨酯处理剂对木粉表面进行处理,并制备了聚氯乙烯(PVC)/木粉复合材料,研究了表面处理剂的交联度、不同用量和高活性反应基团—NCO的含量对复合材料性能及结构的影响。结果表明,使用聚氨酯处理剂对木粉表面进行处理可以明显改善复合材料的流变性能,并明显提高复合材料的力学性能;扫描电镜观察表明,木粉经聚氨酯处理剂改性后与PVC的相容性明显得到改善。     

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 and heat deflection properties of PVC/PMMA/montmorillonite composites

Composites based on PVC were compounded with 5% of montmorillonite and 10% of PMMA. Two types of reinforcement were studied, which included a purified sodium montmorillonite and a montmorillonite organically modified with an alkylammonium chloride. The composites were compounded with a Gelimat type thermokinetic mixer and were ejected at a maximum temperature of 180°C. The organically modified montmorillonite discolored the PVC, result which was interpreted as a sign of chemical degradation caused by the alkylammonium modifier. The composite made with 5% of purified montmorillonite and 10 of % PMMA displayed the best overall properties. The most important improvement was obtained on flexural strain at break (0.097–0.175 mm/mm) and maximum flexural strength (62–76 MPa). The HDT increased by up to 8°C. Dynamic mechanical analysis showed that 10% of PMMA in PVC moved the tan δ peak to temperatures 5–6°C higher. The PMMA was completely miscible in PVC and played an important role in the montmorillonite dispersion, as observed by XRD and SEM analysis. It also contributed to the overall increase in properties of PVC/PMMA/montmorillonite composites. J. VINYL ADDIT. TECHNOL., 13:91–97, 2007. © 2007 Society of Plastics Engineers.