Effect of moisture content on mechanical properties,thermal and structural stability and extrudate texture of poly(vinyl chloride)/wood sawdust composites

Mechanical properties and thermal and structural changes of poly(vinyl chloride) (PVC)/wood sawdust composites were assessed with respect to the effect of moisture content, varying from 0.33 to 3.00 % by weight in the composite, for three different wood sawdust contents. The swell ratio and texture characteristics of the composite extrudates were also evaluated. Unique explanations were given to describe changes in the composite properties in terms of molecular interactions between PVC, cellulosic sawdust and moisture, such as dipole–dipole interactions, interfacial defects and bonding, fibre swelling, and moisture evaporation. The results suggest that at low moisture content the tensile modulus decreased and elongation at break of the composites increased with moisture content, the effect being reversed for high moisture content. Tensile strength decreased with increasing moisture content up to 1–2 %, and then unexpectedly increased at higher moisture contents. The effect of moisture content on flexural properties of the composite was similar to that on tensile properties. Impact strength of the composites was considerably improved with moisture content at low sawdust contents (16.7 wt%), and was independent of the moisture content at higher sawdust contents (28.6 and 37.5 wt%). A decrease in decomposition temperature with an increase in polyene content was evidenced with increasing moisture content, while the glass transition temperature did not change with varying moisture content. The extrudate swell ratio increased with the shear rate but remained unaffected by moisture content. The bubbling and peeling‐off in the composite extrudate occurred as a result of the evaporation of water molecules and the application of a high shear rate. Copyright © 2004 Society of Chemical Industry     

Preparation and characterization of poly(vinyl chloride)–continuous carbon fiber composites

In this article, we report on the preparation and characterization of novel poly(vinyl chloride) (PVC)–carbon fiber (CF) composites. We achieved the reinforcement of PVC matrices with different plasticizer contents using unidirectional continuous CFs by applying a warm press and a cylinder press for the preparation of the PVC–CF composites. We achieved considerable reinforcement of PVC even at a relatively low CF content; for example, the maximum stress (σ_max) of the PVC–CF composite at a 3% CF content was found to be 1.5–2 times higher than that of the PVC matrix. There were great differences among the Young's modulus values of the pure PVC and PVC–CF composites matrices. The absolute Young's modulus values were in the range 1100–1300 MPa at a 3% CF content; these values were almost independent of the plasticizer content. In addition, we found a linear relationship between σ_max and the CF content and also recognized a linear variation of the Young's modulus with the CF content. The adhesion of CF to the PVC matrix was strong in each case, as concluded from the strain–stress curves and the light microscopy and scanning electron microscopy investigations. The mechanical properties of the PVC–CF composites with randomly oriented short (10 mm) fibers were also investigated. At low deformations, the stiffness of the composites improved with increasing CF content. Dynamic mechanical analysis (DMA) was used to determine the glass‐transition temperature (T_g) of the PVC–CF composites. The high increase in the Young's modulus entailed only a mild T_g increase. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Poly(vinyl chloride)–green coconut fiber composites and their nonlinear viscoelastic behavior as examined with fourier transform rheometry

Using a purposely modified torsional dynamic rheometer with a closed cavity, I investigated composites of poly(vinyl chloride) (PVC) and green coconut fibers (GCFs) with Fourier transform (FT) rheometry, a new dynamic test technique that resolves the complex dynamic response of materials submitted to harmonic strain into their main and harmonic components. Because of instrument limitations in the low‐strain region, torque signal harmonic components had to be corrected to yield results that suited established theoretical considerations. The preparation method of the composites had major effects on their linear and nonlinear viscoelastic responses; essentially, no homogeneous material could be prepared by dry blending plus extrusion, in contrast to dry blending plus mixing, which is the recommended technique; this was likely because PVC plasticization was then achieved. One of the most important rheological characteristics of the PVC–GCF composites was the quasidisappearance of the linear viscoelastic behavior. Nevertheless, an easy extrapolation technique was used to extract linear modulus data from the FT results, which led me to the conclusion that the reinforcing effect of the GCFs was essentially hydrodynamic with little, if any, interfacial interaction between the polymer matrix and the fibers. The results gathered from nonlinear viscoelastic properties, as obtained through FT rheometry, supplement this conclusion. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3638–3651, 2006     

Evaluation of the effects of biobased plasticizers on the thermal and mechanical properties of poly(vinyl chloride)

Blends were prepared of poly(vinyl chloride) (PVC) with four different plasticizers; esters of aconitic, citric, and phthalic acids; and other ingredients used in commercial flexible PVC products. The thermal and mechanical properties of the fresh products and of the products after 6 months of aging were measured. Young's modulus of the PVC blends was reduced about 10‐fold by an increase in the plasticizer level from 15 to 30 phr from the semirigid to the flexible range according to the ASTM classification, but a 40‐phr level was required for PVC to retain its flexibility beyond 6 months. At the 40‐phr level, tributyl aconitate performed better than diisononyl phthalate (DINP) or tributyl citrate, in terms of lowering Young's modulus, both in the fresh materials and those aged for 6 months. The effects of the four plasticizers on the glass‐transition temperature (T_g) were similar, with T_g close to ambient temperature at the 30‐ and 40‐phr levels in freshly prepared samples and at 40–60°C in those aged for 6 months. The thermal stability of the PVC plasticized with DINP was superior among the group. Overall, tributyl aconitate appeared to be a good candidate for use in consumer products where the alleged toxicity of DINP may be an issue. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1366–1373, 2006     

Experimental investigations of polypropylene and poly(vinyl chloride) composites filled with plerospheres

Plerospheres, defined here as superfine spherical particles (0.5–5 μm) separated from fly ash (rather than as other solid spherical particles, as some have used the term), are separated from coal fly ash but are dramatically different from it. Plerospheres can be used as polymer fillers to improve the properties of composites. With plerospheres used as fillers for polypropylene (PP) and unplasticized poly(vinyl chloride) (UPVC), the effects of the filler content, the particle sizes of the plerospheres, and the coupling agent on the composite properties were studied. The particle sizes of the plerospheres were 2 and 5 μm. The results suggested that the notched impact properties both at a normal temperature and a low temperature and the tensile and flexural properties of plerosphere/PP increased significantly when the content was increased from 0 to 30 wt % and further increased with the addition of a coupling agent. Differential scanning calorimetry indicated that the thermal properties of the plerosphere/PP composite improved. The surface characteristics and morphology of the impact fracture surface were examined in detail with scanning electron microscopy. The rheological performance of plerosphere/UPVC pipe composites obviously improved; the plasticizing time was shortened, and the maximum torque was reduced. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 126–131, 2004     

Thermal and dynamic mechanical behavior of poly(vinyl chloride)/wood flour composites

Thermal and dynamic mechanical behaviors of wood plastic composites made of poly vinyl chloride (PVC) and surface treated, untreated wood flour were characterized by using differential scanning calorimetry and dynamic mechanical analysis. Glass transition temperature (T_g) of PVC was slightly increased by the addition of wood flour and by wood flour surface treatments. Heat capacity differences (ΔC_p) of composites before and after glass transition were markedly reduced. PVC/wood composites exhibited smaller tan δ peaks than PVC alone, suggesting that less energy was dissipated for coordinated movements and disentanglements of PVC polymer chains in the composites. The rubbery plateaus of storage modulus (E′) curves almost disappeared for PVC/wood composites in contrast to a well defined plateau range for pure PVC. It is proposed that wood flour particles act as “physical crosslinking points” or “pinning centers” inside the PVC matrix, resulting in the absence of the rubbery plateau and high E′ above T_g. The mobility of PVC chain segments were further retarded by the presence of surface modified wood flour. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and mechanical properties of poly(vinyl chloride)/bamboo flour composites with a novel block copolymer as a coupling agent

To improve the interfacial adhesion between poly(vinyl chloride) (PVC) and bamboo flour in PVC/bamboo flour composites, a novel coupling agent, poly(styrene‐co‐maleic anhydride)‐block‐poly(styrene‐co‐acrylonitrile) {P[(SMA)‐b‐(SAN)]}, was synthesized through living free‐radical polymerization in a one‐pot reaction. P[(SMA)‐b‐(SAN)] was synthesized by a nitroxide‐mediated polymerization technique in the presence of 2,2,6,6‐tetramethylpiperidin‐l‐oxyl with azobisisobutyronitrile. The conversion of maleic anhydride (>99%) and styrene (>65%) was relatively high and yielded P[(SMA)‐b‐(SAN)] with a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight <1.38). PVC was blended with bamboo flours in the presence of the synthesized coupling agent with a two‐roll mill. P[(SMA)‐b‐(SAN)] was added to the PVC matrix at a concentration of 55 or 20 wt %. As the content of P[(SMA)‐b‐(SAN)] in the wood–polymer composite increased, improved morphological and mechanical behaviors were observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of plasticizers on mechanical,electrical, permanence,and thermal properties of poly(vinyl chloride)

Effects of three different plasticizers and their blends with dioctyl phthalate (DOP) on thermal stability, flammability, mechanical, electrical, and permanence properties of poly(vinyl chloride) (PVC) compound were studied. Various plasticizers used were DOP, butyl benzyl phthalate (BBP), isodecyl diphenyl phosphate (IDDP), and polybutylene adipate (PBA) at concentrations of up to 40 phr level. Studies showed that processability and softness were improved by addition of BBP. An increase in the content of IDDP increased the electrical and flammability properties, whereas compositions with PBA exhibited the best permanence properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3278–3284, 2003     

Dynamic mechanical and mechanical properties of polypropylene/poly(vinyl butyral)/mica composites

Three-component composites consisting of polypropylene (PP) matrix, poly(vinyl butyral) (PVB) modifier, and mica filler at various ratios of matrix to modifies and a constant mica content (30 wt %) were prepared by using two different kinds of PVB, viz., PVB and PVB-P. By correlating with the morphology, the dynamic mechanical and mechanical properties of the composites are studied in detail. PVB component in PP/PVB/mica composites cannot display a reinforcing effect to PP/mica binary composites, while impact strength of the composites are reduced further. It associates with incompatibility between PP and PVB, and as well as higher glass transition temperature of PVB. For PP/PVB-P/mica composites, stiffness decreases and, meanwhile, impact strength increases when PVB-P content is 7 wt %. The improvement of impact strength on PP/mica binary composites at the composition is due to a little affinity between the PP matrix and the plasticizer of PVB-P. Moreover, a minor amount of PP-g-MA in the 63/7/30 PP/PVB/mica composites only acts as an adhesion promoter. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2003–2011, 1997     

Alloying of poly(vinyl chloride) to reduce plasticizer migration

Concern over the migration of low molecular weight plasticizer from flexible poly(vinyl chloride) (PVC) used in toys and medical products has spearheaded the commercialization of a number of plasticizing polymers. In this study the plasticizing behavior of an ethylene/vinyl acetate/carbon monoxide terpolymer (Elvaloy® from DuPont) was investigated. Blends of PVC, Elvaloy 742, and dioctyl phthalate (DOP) were processed on a twin‐roll mill and compression molded into plaques. These materials were characterized in terms of their hardness, glass‐transition temperature (T_g), clarity, mechanical properties, and plasticizer migration behavior. The ratios of PVC/DOP/Elvaloy investigated were determined by experimental design. Using this approach it was possible to model the results and produce contour plots to map out the properties of a wide range of formulations. It was confirmed that Elvaloy 742 is compatible with PVC and has a plasticizing effect: this was demonstrated both in terms of a reduction in Shore A hardness and a reduction in T_g. Plasticizer migration was reduced in proportion to the amount of liquid plasticizer replaced. Plasticizing with Elvaloy gave an improvement in tear strength. However, at constant hardness there was no improvement in tensile strength from replacing DOP with Elvaloy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2022–2031, 2004     

Thermal stability of poly(vinyl chloride)/layered double hydroxide nanocomposites

Effects of nanoscale dispersed layered double hydroxides (LDHs) on thermal stability of poly(vinyl chloride) (PVC) in thermal and thermooxidative degradation processes are investigated by dynamic and isothermal thermogravimetric analysis (TGA), discoloration test, fourier transform infrared (FTIR), and ultraviolet‐visible (UV‐vis) spectroscopic techniques. During both stages of thermal degradation, the degradation temperatures, including onset degradation temperature and temperature of the maximum degradation rate, increase, and the final residue yield of the PVC/LDH nanocomposites reaches 14.7 wt %, more than double that for neat PVC. The thermooxidative degradation process is more complex. During the first two stages, the presence of nanoscale dispersed LDH particles enhances the thermal stability, whereas in the last stage accelerates the thermal degradation possibly due to the accumulation of heat released. Additionally, the studies of the isothermal thermooxidative degradation process by FTIR and UV‐vis spectra indicate that both polyene backbone formation and some carbonyl groups are simultaneously developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A new biobased plasticizer for poly(vinyl chloride) based on epoxidized cottonseed oil

The use of epoxidized cottonseed oil as plasticizer for poly(vinyl chloride) was studied. The plasticizer content was set to 70 phr and the optimum isothermal curing conditions were studied in the temperature range comprised between 160 and 220 °C with varying curing times in the 7.5–17.5 min range. The influence of the curing conditions on overall performance of cured plastisols was followed by the evolution of mechanical properties (tensile tests with measurements of tensile strength, elongation at break, and modulus), change in color, surface changes of fractured samples by scanning electron microscopy (SEM), thermal transitions by differential scanning calorimetry, and migration in n‐hexane. The optimum mechanical features of cured plastisols are obtained for curing temperatures in the 190–220 °C range. For these curing conditions, fractography analysis by SEM gives evidences of full curing process as no PVC particles and free plasticizer can be found. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43642.     

Studies of electrical and mechanical properties of semiconductive poly(vinyl chloride) compositions

A sample of poly(vinyl chloride) (PVC) and a polar plasticizer consisting of dioctylphthalate (DOP) and triisopropylphenylphosphate (TIPPP) was prepared and found to possess some electrical conductivity. Different samples of PVC compositions were formulated from the PVC-DOP-TIPPP system and also variable proportions of the conductive materials polyaniline or the Ni salt of ethylene glycol bisadipate ester. Dibutyltindilaurate as a heat stabilizer, titanium oxide as a filler, and sandorin red 20 pigment were added. The effect of the structure of polyaniline and Ni adipate ester on the electrical and mechanical properties of the PVC–DOP–TIPPP system was studied to obtain a semiconductive plasticized PVC with good mechanical properties. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 685–693, 1998     

Miscibility and rheological properties of poly(vinyl chloride)/styrene–acrylonitrile blends prepared by melt extrusion

Styrene–acrylonitrile (SAN) with acrylonitrile (AN) concentrations of 11.6–26 wt % and α‐methylstyrene acrylonitrile (αMSAN) with a wide range of AN concentrations are miscible with poly(vinyl chloride) (PVC) through solution blending. Here we examine the rheological properties and miscibility of PVC/SAN and PVC/αMSAN blends prepared by melt extrusion for commercial applications. We have investigated the rheological properties of the blends with a rheometer and a melt indexer. The PVC/SAN and PVC/αMSAN blends have a low melting torque, a long degradation time, and a high melt index, and this means that they have better processability than pure PVC. The miscibility of the blends has been characterized with differential scanning calorimetry, dynamic mechanical thermal analysis, and advanced rheometrics expansion system analysis. The miscibility of the blends has also been characterized with scanning electron microscopy. The SAN series with AN concentrations of 24–31 wt % is immiscible with PVC by melt extrusion, whereas αMSAN with 31 wt % AN is miscible with PVC, even when they are blended by melt extrusion, because of the strong interaction between PVC and αMSAN. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of poly(epichlorohydrin) on the thermal and mechanical properties of poly(vinyl chloride)

Five kinds of polyepichlorohydrin (PECH) of different molecular weights were synthesized and characterized by gel permeation chromatography (GPC). Mechanical blending was used to mix PECH and poly(vinyl chloride) (PVC) together. The blends of different PVC/PECH ratios were characterized by thermogravimetric analysis (TGA), tensile tests, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). TGA results show the thermal stability of PVC/PECH blends is desirable. Tensile tests indicate elongation at break is raised by increasing both the amount and the molecular weight of PECH. DSC is used to determine the glass transition temperature of PECH, and a quite low T_g is obtained. DMA results indicate that PECH has a perfect compatibility with PVC, when PECH concentration is below 20 wt %. There is only one peak in each tan δ curve, and the corresponding T_g decreases as PECH amount increases. However, above 20 wt %, phase separation takes place. The molecular weight of PECH also has a great influence on the glass transition temperature of the blends. This study shows that PECH is an excellent plasticizer for PVC, and one can tailor the glass transition temperature and tensile properties by changing the amount and the molecular weight of PECH. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Processing thermal stability and degradation kinetics of poly(vinyl chloride)/montmorillonite composites

Thermal stability of polyvinyl chloride (PVC) based montmorillonite composites with either sodium montmorillonite (MMT) or alkyl ammonium ion modified montmorillonite (OMMT) were investigated by thermogravimetric analysis. The apparent activation energies associated with the first thermal degradation stage were calculated by the methods of Flynn–Wall–Ozawa and Kissinger in nitrogen atmosphere at several different heating rates. The processing thermal stability of PVC and PVC/MMT(OMMT) composites was also discussed. Increase of mixing torque did not result in a larger intercalation extent of PVC on MMT; instead, it unexpectedly induced discoloration of PVC and then deteriorated the processing stability, especially in the presence of OMMT. The apparent activation energies in the first thermal degradation stage exhibited little difference among PVC, PVC/MMT, and PVC/OMMT composites, and the kinetic compensation effect of S_p^* kept a constant value, indicating that the thermal stability and thermal degradation mechanism of PVC were not affected by the presence of either MMT or OMMT, although the processing discoloration of PVC is observed for PVC/OMMT composite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1521–1526, 2004     

Improving mechanical properties of poly(vinyl chloride) by doping with organically functionalized reactive nanosilica

Nanosilica particles are functionalized by in situ surface‐modification with trimethyl silane and vinyl silane. Resultant reactive nanosilica (coded as RNS) contains double bonds and possesses good compatibility with vinyl chloride (VC) and polyvinyl chloride (PVC). This makes it feasible for RNS to copolymerize with VC generating RNS/PVC composites via in situ suspension polymerization. As‐prepared RNS/PVC composite resins are analyzed by means of FTIR. The tensile strength and impact strength of compression‐molded RNS/PVC composites are measured and compared with that of compression‐molded PVC composites doped with dispersible nano‐SiO₂ particles (abridged as DNS) surface‐modified with trimethyl silane alone. Moreover, the thermal stability of compression‐molded RNS/PVC and DNS/PVC composites is evaluated by thermogravimetric analysis. It has been found that RNS/PVC composites possess greatly increased impact strength and tensile strength than PVC matrix, while DNS/PVC composites possess higher impact strength than PVC matrix but almost the same tensile strength as the PVC matrix. This implies that DNS is less effective than RNS in improving the mechanical strength of PVC matrix. Particularly, RNS/PVC composites prepared by in situ suspension polymerization have much higher mechanical strength than RNS/PVC composites prepared by melt‐blending, even when their nanosilica content is only 1/10 of that of the melt‐blended ones. Besides, in situ polymerized RNS/PVC and DNS/PVC composites have better thermal stability than melt‐blended nanosilica/PVC composites. Hopefully, this strategy, may be extended to fabricating various novel high‐performance polymer‐matrix composites doped with organically functionalized nanoparticles like RNS. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanochemical improvement of the flame‐retardant and mechanical properties of zinc borate and zinc borate–aluminum trihydrate‐filled poly(vinyl chloride)

In this study, the effect of the high‐energy mechanical milling of a mixture of poly(vinyl chloride) (PVC) with zinc borate (ZB) or ZB–aluminum trihydrate (ATH), a mixture of ZB and ATH, on the flame‐retardant and mechanical properties of ZB and ZB–ATH filled PVC was examined. The high‐energy mechanical milling of PVC/ZB and the PVC/ZB–ATH mixture produced chemical bonding between PVC and ZB or ZB–ATH, increasing the interfacial interaction of PVC/ZB and PVC/ZB–ATH blends, which resulted in a great increase in the limiting oxygen index, the impact and yield strengths, and the elongation at break of PVC/ZB and PVC/ZB–ATH blends. The results from ultraviolet spectroscopy and gas chromatography–mass spectroscopy show that mechanochemical modification of ZB and ZB–ATH much more effectively suppressed the release of aromatic compounds in PVC/ZB and PVC/ZB–ATH blends during burning. Mechanochemical modification provided an excellent route for the improvement of the flame‐retardant and mechanical properties of flame‐retardant‐additive‐filled PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 753–762, 2003     

Synthesis of glycidylethylhexylphthalate and its effects on poly(vinyl chloride) films as a novel plasticizer

To improve the processability and prevent the thermal degradation of poly(vinyl chloride) (PVC), various plasticizers and heat stabilizers have to be compounded. Phthalic plasticizers and metal soap stabilizers are usually used with epoxides as costabilizers. Epoxidized soybean oil (ESO), is one of the most commonly used epoxides because of its typical combined roles as a plasticizer and heat stabilizer in PVC compounds. ESO, however, sometimes causes surface contamination of PVC compounds because saturated fatty acids such as stearic and palmitic acids in soybean oil easily bleed onto the surface. In addition, some ingredients in ESO with hydroxide groups and unreacted double bonds during epoxidization also tend to increase the bleeding of ESO. This is due to their low compatibility with PVC resins. In this study, a novel plasticizer of PVC resins, glycidylethylhexylphthalate (GEHP), was synthesized, and its performance was evaluated. GEHP was designed to act as a plasticizer like normal phthalic plasticizers and to act as a heat stabilizer like ESO. Through the addition of epoxy groups in phthalic compounds, the resistance to bleeding was improved, and the plasticizing and heat‐stabilizing effects on the PVC compounds were preserved. Soft PVC films were prepared with GEHP. The mechanical properties, thermal stability, and bleeding properties of the films were investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1347–1356, 2005     

Behavior of flexible poly(vinyl chloride)/poly(hydroxybutyrate valerate) blends

Blends of flexible poly(vinyl chloride) (PVC) and a poly(hydroxybutyrate valerate) (PHBV) copolymer were prepared and characterized with different techniques. The tensile strength of PVC did not show a marked reduction at PHBV concentrations up to 50 phr, despite a lack of miscibility between the two polymers. The crystallization of the PHBV copolymer was markedly hindered by the presence of PVC, as calorimetric results revealed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008