Effect of crosslinking on the mechanical and thermal properties of poly(vinyl alcohol)

Poly(vinyl alcohol) was crosslinked with hexamethylene diisocyanate in solution. A broad range of degrees of crosslinking, from 1.7 up to 74 mol% of reacted hydroxyl groups, was achieved. The variation of the thermal and mechanical properties of PVA with the crosslinking density show an initial decrease due to the diminution of the crystallinity of the system, caused by the crosslinking. After an abrupt rise at about 20%, the properties tend to level off independently on the increase of the crosslinking. This behaviour is explained as a result of the competitive action of at least three factors during the crosslinking: (i) weakening of the existing physical network due to hydrogen bonding; (ii) formation of a chemical network; and (iii) introduction of flexible moieties. The last factor is closely connected with the specific chemical structure of the crosslinker itself.     

Effects of gamma irradiation on the thermal and mechanical properties of chitosan/PVA nanofibrous mats

Chitosan/poly(vinyl alcohol) (PVA) nanofibrous mats were prepared by the electrospinning method. The morphology and structure of electrospun nanofibers were investigated by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. SEM images showed that the uniform and bead-free fibers were obtained at concentrations greater than 8 wt%. Chitosan/PVA mats were irradiated with different doses (50–200 kGy) of ⁶⁰Co gamma rays. The effect of irradiation dose on the mechanical and thermal properties of these films was also investigated. Increasing the irradiation dose led to a decrease in tensile strength. FT-IR and DSC demonstrated that there were strong intermolecular hydrogen bonds between the chitosan and PVA molecules.     

PA6/PVA共混物的相容性与力学性能研究

制备了聚酰胺6/聚乙烯醇(PA6/PVA)共混物,通过DMA、FTIR、DSC和力学性能测试等方法对共混物进行了表征,利用Hoffman-Weeks方程和Flory熔点下降方程求得了PA6的平衡熔点和两种聚合物的相互作用参数,研究了共混物的相容性和力学性能。结果表明:在氢键的作用下,PA6/PVA共混物具有良好的相容性;PA6与PVA相互作用参数为-0.085,进一步证明了PA6/PVA共混物是热力学相容体系;当PVA含量为50%时,PA6/PVA共混物的相容性和力学性能最佳。     

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     

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     

Degree of crosslinking and mechanical properties of crosslinked poly(vinyl alcohol) beads for use in solid-phase organic synthesis

The limited swellability in polar media of the commonly used polystyrene/divinylbenzene (PS-DVB) support materials for solid-phase organic synthesis has led to the development of novel, highly swellable hydrophilic gels designed for use in aqueous or polar media. Poly(vinyl alcohol) beads crosslinked with epichlorohydrin (PVA-EP) were prepared by a two-step inverse-suspension polymerization method. While it is known that the morphology of the resulting beads can be controlled by the ratio of EP versus PVA as well as by the pre-crosslinking time, the actual degree of crosslinking of the beads and their mechanical properties remain unknown. It is therefore the purpose of this study to evaluate the actual degree of crosslinking of beads prepared with different quantities of crosslinker in the feed by spectroscopic (Raman, nuclear magnetic resonance) and chemical (functional group loading) methods. The mechanical properties of these swollen PVA-EP beads will be evaluated by single-bead unconfined compression in solvents such as water, N,N-dimethylformamide (DMF), and tetrahydrofuran (THF) and compared to model PS-DVB beads commonly used for solid phase synthesis.     

Plasma treatment for enhancing mechanical and thermal properties of biodegradable PVA/starch blends

Two series of biodegradaable polyvinyl alcohol (PVA)/starch blends, i.e., PVA with/without plasma treatment (PP/P series), were produced by single‐screw extruder. The influences of plasma pretreatment and PVA content on the tensile properties, thermal behaviors, melt flow index, and biodegradability of blends were investigated. PVA pretreated by plasma (PPVA) reacted with glycerol was found not only to mechanically strengthen the PPVA/starch blend but also to improve the compatibility of PPVA and starch. Compared with PVA/starch blends, the melt flow indices of PPVA/starch blends were improved significantly by 200–300% and their tensile strength also increased two‐to‐three‐fold. Thermogravimetry analysis (TGA) showed that the thermal stability of PPVA/starch (85/300g) blend was better than PVA/starch blend at processing temperature and outperformed than PVA and starch at high temperature. Both the PPVA/starch and PVA/starch blends finished biodegradation within 9–10 weeks in soil burial tests. The esterification reaction of PPVA and glycerol was characterized by FTIR spectroscopic measurement and TGA test. The morphologic evolutions of the blend during biodegradation were investigated carefully by scanning electron microscope (SEM) imaging. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of hydrotalcite on the thermal stability,mechanical properties,rheology and flame retardance of poly(vinyl chloride)

Compounds of poly(vinyl chloride) (PVC) and hydrotalcite were prepared via melt blending, and the thermal stability, mechanical properties, rheology and flame retardance were studied. Transmission electron microscopy showed that the hydrotalcite achieved an optimal dispersion in PVC compounds when surface‐treated with titanate coupling agent. The Congo Red test and thermogravimetric analysis demonstrated that the thermal stability of PVC was improved significantly only in the presence of a complex of the hydrotalcite and the organotin stabilizer. Such a significantly positive thermal stabilizing effect was attributable to the stabilizing mechanisms that the electrostatic interaction generated between the electron cloud of chlorine atoms in PVC chain and the positive lay charge of hydrotalcite, which resulted in a decrease in electronic cloud density of chlorine atoms. This weakened the activity of chloride atoms, and restricted the initiation of the dehydrochlorination. A surface treatment for the hydrotalcite with the titanate coupling agent could reduce deterioration of the mechanical and rheological properties of the PVC at low concentration of hydrotalcite. The hydrotalcite also enabled useful application of PVC as a flame retardant as well as a smoke retarder in the light of a LOI value of more than 28.7 and UL 94 V‐0 grade at a PVC/hydrotalcite weight ratio of 70/30. Copyright © 2004 Society of Chemical Industry     

Effect of zinc maleate/zinc oxide complex on thermal stability of poly(vinyl chloride)

In this study, zinc maleate (ZnMA) and zinc oxide (ZnO) complex (ZnMA/ZnO) was prepared by two methods, namely, by the reaction of maleic acid (MAH) with excess ZnO in aqueous solution and by direct mixing of ZnMA and ZnO at 180°C. The chemical structure of the complex was analyzed by X‐ray diffraction, thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectroscopy. The thermal stabilizing effect of the complex on poly(vinyl chloride) (PVC) was evaluated through static and dynamic stability methods. Compared to calcium and zinc soaps and ZnMA alone, the complex exhibited better thermal stabilizing effect on PVC. The stabilization mechanism was also investigated by ultraviolet–visible spectrometer, FTIR, TGA, and gel content analysis. The results indicated that the complex which involved the replacement of labile chlorine atoms hindered the formation of conjugated double bonds in PVC chains via Diels–Alder reaction, and ZnMA/ZnO complex also exhibited the ability to absorb hydrogen chloride. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41464.     

CaCl2·6H2O/多孔Al2O3复合相变材料的制备与热性能

将CaCl2·6H2O作为相变材料,3%的硼砂作为成核剂,以多孔Al2O3作为基体,通过真空浸渍法和多孔Al2O3的毛细吸附作用,制得不同比例的CaCl2·6H2O/多孔Al2O3复合相变材料,并进一步对其微观结构和热性能进行了分析。N2吸附脱附等温线分析证明,多孔Al2O3具有较大的比表面积。SEM照片和FTIR光谱说明CaCl2·6H2O被成功吸附入Al2O3的多孔结构中。DSC曲线显示,复合相变材料的熔融潜热可达99.81 J/g,说明其具有良好的相变储热性能。     

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     

六水氯化镁在六种多元醇中溶解度的测定和关联

六水氯化镁的溶解度是镁盐综合利用的重要基础数据。采用静态平衡法测定了六水氯化镁在1,2-丙二醇、1,3-丙二醇、1,3-丁二醇、一缩二乙二醇、二缩三乙二醇、一缩二丙二醇6种多元醇中的溶解度（278.15~328.15 K）。实验结果表明,六水氯化镁在6种多元醇中的溶解度均随着温度的升高而增大,其中在一缩二乙二醇中的溶解度最大,在二缩三乙二醇中的溶解度随着温度的变化较其他多元醇变化更为明显。使用Apelblat方程、λh方程、Van′t Hoff方程和多项式方程对溶解度数据进行了关联,结果良好,其中Apelblat方程和多项式方程拟合结果优于其他方程。利用Van′t Hoff方程计算了6种体系的溶解焓、溶解熵和吉布斯自由能。这些结果对镁盐的分离提取及镁基功能材料的制备具有重要的参考价值。     

Functionalized polyvinyl chloride/layered double hydroxide nanocomposites and its thermal and mechanical properties

In this work, to inquire the impact of layered double hydroxide (LDH) nanoclay on functionalized poly(vinyl chloride) (PVC) through solution intercalation method, four kinds of nanocomposites were prepared. Mg-AL LDH and the obtained functionalize PVC composites were characterized through FT-IR, UV–Vis spectroscopy, TEM, XRD, contact angle, DSC, and UTM. Obtained results revealed that the functionalized PVC uniformly dispersed in the layer of LDH nanoclay. It is revealed that partially intercalated and disordered structure formed in PVC/LDH, PVC-TS (thiosulfate)/LDH, and PVC-S (sulfate)/LDH nanocomposites, whereas fully exfoliated structures formed in the PVC-TU (thiourea)/LDH nanocomposites. Further, it has been observed that the ultimate tensile strength for all the polymer nanocomposites enhanced with increased in the LDH content. These nanocomposites further exhibited higher thermal stability by at least by 51°C higher than the pristine PVC. Along with these, further it has been found that the functionalized PVC/LDH nanocomposites are proved to be effective as thermal stabilizer for PVC processing. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48894.     

Effect of glycerol on thermal and mechanical properties of polyvinyl alcohol/starch blends

The paper reports the results of studies on the effect of glycerol content on thermal, mechanical, and dynamic mechanical properties of blends of starch and polyvinyl alcohol (PVA). Degree of crystallinity of the starch/PVA blends (4 g/4 g ratio) remains almost constant up to 3.78 g of glycerol as determined by differential scanning calorimetry (DSC) and x‐ray diffraction studies. At higher loading of glycerol the crystallinity decreases. DTG thermograms revealed occurring of one maximum degradation temperature closer to that of starch in blends containing up to 3.78 g of glycerol. At higher glycerol content there gradually occur two distinct peaks of maximum degradation temperature, one occurring close to that of starch and other occurring close to the PVA peak, indicating phase separation of the blend components. Results of stress–strain studies indicate lowering of tensile properties and energy at break particularly at higher glycerol content (beyond 3.78 g). Dynamic mechanical studies reveal a sharp drop in dynamic modulus at higher glycerol content at all temperatures. The blend with low glycerol content shows transitions of starch, while the blend containing high glycerol content beyond 3.78 g display the transitions due to both starch and PVA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of thermal aging on the electrical properties of poly(vinyl chloride)

This article reports on the study of the thermal aging of poly(vinyl chloride) (PVC) used in medium‐ and high‐voltage cables. It is shown that the thermal aging leads to the degradation of the material and to the modification of its electrical properties. The degradation is all the more important and faster as the temperature is high. This degradation is attributed to a progressive evaporation of the plasticizer at the beginning of aging and to a weight loss of stabilizer followed by a change in the color of polymer and a release of hydrochloric acid at more advanced stages of aging. It also results in a crosslinking of the material and a shrinking of samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4728–4733, 2006     

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     

Crosslinked poly(vinyl alcohol) and starch composite films. II. Physicomechanical,thermal properties and swelling studies

Poly(vinyl alcohol) (PVA) was blended with 10, 20, 30, 40, and 50 wt % of starch with and without crosslinking by solution casting process. The solution‐casted films were dried and tested for physicomechanical properties like tensile strength, tensile elongation, tensile modulus, tear and burst strengths, density, and thermal analysis by differential scanning calorimetry (DSC). These PVA/starch films were further characterized for moisture content; solubility resistance in water, 5% acetic acid, 50% ethanol, and sunflower oil; and swelling characteristics in 50% ethanol and sunflower oil. The crosslinked PVA/starch composite films show significant improvement in tensile strength, tensile modulus, tear and burst strengths, and solubility resistance over the uncrosslinked films. Between the crosslinked and uncrosslinked films, the uncrosslinked films have higher tensile elongation, moisture content, moisture absorption, and swelling over the crosslinked films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 909–916, 2007     

聚乙烯醇吹膜加工性能研究

研究了聚乙烯醇(PVA)吹膜加工性能。经两种不同的增塑剂复配增塑后，可明显改善其加工流动性，当复合增塑剂用量为25phr以上，PVA可以被较好地增塑，熔融塑化温度趋于定值。热性能研究表明，PVA为不完全结晶，其熔融曲线呈不规则分布。从PVA的流变性能可知，PVA熔体呈非牛顿性流体，剪切粘度随剪切速率增加而下降，并且醇解度较高的树脂，剪切粘度也较高。不同醇解度的PVA树脂，均能通过增塑改性后熔融挤出加工吹塑成膜。高醇解度PVA膜的水溶解温度高，而低醇解度PVA膜具有低温快速水解的性能。     

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     

Effect of lignin esters on improving the thermal properties of poly(vinyl chloride)

To improve the thermal stability of poly(vinyl chloride) (PVC) and the utilization of lignin (L), different L esters were added to PVC to produce the plates with enhanced thermal stabilities. The properties and structures of the L ester–PVC plates and the properties of the L esters and their mixtures with PVC were analyzed by universal mechanical testing, static thermal stability testing, thermogravimetry–Fourier transform infrared (FTIR) spectroscopy, UV–visible spectroscopy, FTIR spectroscopy, scanning electron microscopy, and differential scanning calorimetry. The results show that L improved the thermal stability of PVC, but the mechanical properties were substantially deteriorated. Proper esterification of L improved the thermal stabilities and mechanical properties of the plates. Noncyclic anhydride acetylated L–PVC plates possessed good static and dynamic thermal stabilities and mechanical properties. The PVC plates incorporated with the L esters with a degree of esterification of around 40% exhibited the best combination properties. Maleated L–PVC plates had good dynamic thermal stability and mechanical properties but poor static thermal stability. The opposite properties were found for succinylated L–PVC plates. The differences in the properties of different L ester–PVC plates were attributed to the different abilities of L esters to capture free radicals, the crosslinking reaction between L esters and PVC, and their compatibility. Different properties of the L esters indicated their different applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47176.