Effect of urea and formamide plasticizers on starch/PVA bioblend sheets

The starch/polyvinyl alcohol (PVA) bioblend sheets containing urea and formamide as plasticizers were prepared through melt processing in presence of water. The experiments indicated that urea and formamide plasticizers could form strong hydrogen bonds with starch/PVA molecules. Urea exhibited better plasticizing effect than formamide. Urea also could greatly destroy the crystal structures of PVA component in the blends, leading to the decreased crystallinity of the blends. Formamide was a good solvent for urea and could prevent urea separating from the blends, resulting in the improved stability of plasticizing systems. The blends exhibited good flexibility. Therefore, the incorporation of both urea and formamide into starch/PVA blends could exhibit synergistic effects to ensure the blends with both good plasticizing effect and the stability of the plasticizing systems. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42311.     

改性PVA热塑加工性能研究

采用熔体流动速率试验机研究了以水、甘油、聚乙二醇和己内酰胺为主的四种加工改性剂对聚乙烯醇(PVA)热塑加工性能的影响。采用平板硫化机压膜观察不同改性PVA体系的成膜性能。结果表明,加工改性剂在不同程度上改善了PVA的热塑加工性能,其中己内酰胺改性PVA体系具有最好的热塑加工性能;通过热压成型可以将改性PVA制成透明性很好的薄膜;熔体流动速率试验机可以有效地判断PVA改性体系的热塑加工性能。     

Water states and thermal processability of boric acid modified poly(vinyl alcohol)

To further improve the processability of water plasticized poly(vinyl alcohol) (PVA), boric acid (BA), which can rapidly form reversible crosslinked structure with the hydroxyl groups of PVA, was adopted as a modifier, and the water states, thermal performance, and rheological properties of modified PVA were investigated. The results showed that ascribing to the formation of the crosslinked structure between PVA and BA, the content of nonfreezing water in system increased, indicating that the bondage of PVA matrix on water enhanced, thus retarding the tempestuous evaporation of water in system during melt process and making more water remained in system to play the role of plasticizer. Meanwhile, this crosslinked structure shielded part hydroxyl groups in PVA chains, leading to the further weakening of the self‐hydrogen bonding of PVA, and guaranteeing a lower melting point and higher decomposition temperature, thus obtaining a quite wide thermal processing window, i.e., ≥179°C. The melt viscosity of BA modified PVA slightly increased, but still satisfied the requirements for thermal processing, thus reinforcing the flow stability of the melt at high shearing rate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43246.     

淀粉/PVA生物降解材料的热塑性研究

将聚乙烯醇(PVA)、淀粉、增塑剂在Hakke流变仪中共混制备了热塑性淀粉/PvA材料,研究了2种PVA-PVA1799、PVA1788,2种淀粉-玉米淀粉、木薯淀粉的热塑性情况;比较了甘油、乙二醇、乙酰胺3种增塑剂的增塑效果.结果表明:采用合适的增塑剂与适当的PVA、淀粉组合可以使PVA/淀粉共混体系在高温下热塑成型...     

己内酰胺/氯化镁复配增塑聚乙烯醇的性能研究

采用己内酰胺/氯化镁为复配增塑剂,通过流延法制备出了增塑改性的聚乙烯醇(PVA)膜。采用DSC、TGA、XRD分析和力学性能与熔体流动性能测试的方法考察了己内酰胺/氯化镁复配增塑剂对PVA性能的影响。结果表明:氯化镁与己内酰胺复配具有良好的协同增塑效应,其对PVA的增塑效果优于单独使用己内酰胺;复配增塑剂能够有效破坏PVA分子间的氢键,降低PVA的结晶度;加入复配增塑剂后,PVA的熔点降低,热稳定性提高,熔体流动性有所改善,拉伸强度降低,断裂伸长率上升。     

Effects of Plasticizing on Mechanical and Viscous Characteristics of Poly(vinyl alcohol): A Comparative Study between Glycerol and Diethanolamine

Although plasticizing materials by modification with small-molecular chemicals has been extensively utilized in the industrial community, processing poly(vinyl alcohol) (PVA) at high concentrations (C_PVA) or with a high degree of polymerization (DP) remains challenging. Optimization the plasticizing conditions is one means of addressing this issue. In this study, two types of frequently used plasticizers, glycerol (GLY) and diethanolamine (DEA), are chosen to plasticize PVA resin with a DP of 2400. Both PVA/plasticizer films possess excellent optical transmittance and mechanical ductility, whereas the films blended with DEA exhibit higher strength than the PVA/GLY films. The viscosity variation in the temperature (T_op)–C_PVA space is monitored by real-time viscous flow testing, demonstrating that DEA is more effective for reducing the viscosity of PVA, which should improve the processability, facilitating film-forming from concentrated solutions. Furthermore, density functional theory calculations and molecular dynamics simulations illustrate that the PVA/DEA system has a lower binding energy, longer hydrogen bond length, and higher isotropic diffusion coefficient, indicating a stable hydrogen bond network and homogenous dispersion of the plasticizer, leading to good solution fluidity and mechanical performance. This study is significant for guiding the design and manufacture of optically transparent, high-performance PVA films as polarizer precursor.     

大豆分离蛋白的化学改性和增塑研究

研究了尿素、氢氧化钠和二甲基二氯硅烷对大豆分离蛋白的化学改性以及甘油、聚乙二醇、山梨醇、己内酰胺、乙酰胺对改性蛋白质材料的增塑作用。采用红外光谱对改性蛋白质进行了表征,并测试了改性蛋白质的热性能、力学性能、流变性能及耐水性能。结果表明,强碱可以有效地截断蛋白质分子的长链结构,提高蛋白质分子的加工流动性;尿素和二甲基二氯硅烷与蛋白质分子中的亲水基团发生反应或遮盖了蛋白质分子中的亲水基团,从而提高了大豆分离蛋白的耐水性;聚乙二醇和己内酰胺是效果较好的增塑剂。     

聚乙烯醇熔融加工的改性方法研究进展

聚乙烯醇(PVA)是一种含有大量羟基的线形大分子聚合物,羟基能形成大量的分子内和分子间氢键,使纯PVA的熔融温度高于其分解温度,使其难以熔融加工。主要介绍了PVA熔融加工的改性方法,并叙述了其研究和发展状况,指出开发可熔融加工PVA的现实意义。通过对PVA的改性,可以在一定程度上降低PVA熔融温度,实现熔融加工,这样可以提高PVA的产量。随着国民经济的发展和人民生活水平的日益提高,PVA的应用会越来越广泛。     

Preparation and properties of poly(vinyl alcohol) films using carbohydrates as plasticizers

Three nontoxic carbohydrates (ribose, xylose, fructose) were used as poly(vinyl alcohol) (PVA) plasticizers to prepare PVA films using a casting method. Fourier transform infrared spectra demonstrated that hydrogen bonds formed between the carbohydrate and PVA. The crystallinity of raw PVA and PVA film plasticized by carbohydrate was characterized by X‐ray diffraction. Differential scanning calorimetry showed that carbohydrate decreased the melting point (T_m) of PVA. The decomposition temperature of PVA increased with addition of carbohydrate. The thermal stability of PVA film plasticized by carbohydrate (CAPF) was higher than that of PVA film plasticized by glycerol (GLPF). The thermal processing window of CAPF was broader than that of GLPF. The water vapor resistance of CAPF was better than that of GLPF. The mechanical properties of PVA films stored at different relative humidity were studied. Generally, the tensile strength of CAPF was larger than that of GLPF, while the elongation at break of CAPF was close to that of GLPF. Our experimental results indicate that carbohydrates are effective plasticizers for PVA. J. VINYL ADDIT. TECHNOL., 25:E181–E187, 2019. © 2018 Society of Plastics Engineers     

Thermal and surface characterization of plasticized starch polyvinyl alcohol blends crosslinked with epichlorohydrin

Starch‐polyvinyl alcohol (PVA) blends in 2:8 wt % were prepared with various plasticizers such as polyethylene glycol (PEG‐200, PEG‐400) and glycerol. The crosslinking of starch‐PVA blends by epichlorohydrin was carried out in the presence of a plasticizer in situ. The obtained films were analyzed by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), dynamic mechanical and thermal analysis (DMTA), and X‐ray photoelectron spectroscopy (XPS), and remarkable changes in thermal stability and glass‐transition temperature have been observed on plasticizing and crosslinking in different concentrations. Different kinetic models such as Coats–Redfern, Broido, Friedman, and Chang were used to calculate the kinetic parameters of thermal decomposition. The results suggest that the thermal stability and activation energy of thermal decomposition passes through maxima at a critical concentration of plasticizer and increases with increasing crosslinker concentration. High‐resolution C 1s XPS analysis was used to provide a method of differentiating the presence of various carbons associated with different environment in the films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 25–34, 2006     

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     

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。     

Plasticizing effect of glyceryl tribenzoate,dipropylene glycol dibenzoate,and glyceryl triacetate on poly(lactic acid)

The aim of this article is to compare the plasticizing effect of different plasticizers on poly(lactic acid) (PLA) including glyceryl tribenzoate (GTB), dipropylene glycol dibenzoate (DPGDB), and glyceryl triacetate (GTA). The chemical structures of plasticizers are characterized by ¹H‐nuclear magnetic resonance. PLA is blended with GTA, DPGDB, and GTB at various contents by using a twin screw extruder. Plasticizing effect of three plasticizers are evaluated by comparison of thermal property, storage stability, melt plasticizing coefficient, thermal degradation, and water vapor permeability. This study reveals that PLA/DPGDB exhibits better physical properties than the others do. DPGDB containing ether and ester groups may therefore render good compatibility with PLA. POLYM. ENG. SCI., 56:1399–1406, 2016. © 2016 Society of Plastics Engineers     

Structural performance of alkali/acid-ultrasound modified Agave fibers during the melt mixing process with polyvinyl alcohol

This study aims to investigate changes in the structural properties of alkali/acid-ultrasound modified Agave fibers and their performance immersed on a polyvinyl alcohol (PVA) matrix with plasticizer during melt mixing processing. Structural analysis revealed that ultrasound enhances the effectiveness of the conventional alkaline/acid treatments to modify fibers since the simultaneous treatment increased the partial removal of lignocellulosic components, water molecules, and amorphous regions which improved their processability on a PVA matrix. Specific energy consumption values indicated that during melt mixing the modified fibers required more energy to expose the chains of cellulose fraction to function as an interaction site for PVA chains. Once the mixture was homogenized, the fiber-matrix interactions promoted high viscosity, friction, and mechanical stress in the chamber. Therefore, the modified fibers restricted the interaction between plasticizer and PVA in the obtained films, resulting in a highly structured, and reinforced network, increasing the storage modulus as dynamic mechanical analysis indicated. These findings highlight a feasible way to valorize Agave fibers and allow the understanding of the matrix-fiber interactions during melt mixing processing, useful to predict the structural and mechanical properties of the films.     

Formation of the first injectable poly(vinyl alcohol) hydrogel by mixing of functional PVA precursors

In this study we describe the development of an injectable, in situ chemical hydrogel forming system. The gelation occurs under neutral pH and at room temperature immediately upon mixing of the two aqueous poly (vinyl alcohol) components specifically derivatized through carbamate linkages with aldehyde (PVA‐AL) and hydrazide (PVA‐HY) functional groups, respectively. Aldehyde and hydrazide pendant groups were incorporated with a low degree of substitution (DS) into the PVA backbone to keep PVA structural homogeneity minimally altered. As a result, the hydrazone crosslinks are formed rapidly between aldehyde and hydrazide pendant groups when the correspondingly modified PVA components are brought in contact as water solutions. To assess in situ hydrazone crosslinks formation for in vitro cytocompatibility, murine neuroblastoma N2a cells were suspended in cell culture medium with the dissolved PVA‐HY prior to addition to the PVA‐AL aqueous solution. Thus, the cells were chemically encapsulated in a polymer network that was formed by mixing of the corresponding aqueous solutions of PVA functional precursors. Biochemical analysis revealed that cells survived chemical crosslinking and remained viable in the hydrogel for 4 days of culture. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effects of water on drawability,structure, and mechanical properties of poly(vinyl alcohol) melt‐spun fibers

Poly(vinyl alcohol) (PVA) melt‐spun fibers with circular cross‐section and uniform structure, which could support high stretching, were prepared by using water as plasticizer. The effects of water content on drawability, crystallization structure, and mechanical properties of the fibers were studied. The results showed that the maximum draw ratio of PVA fibers decreased with the increase of water content due to the intensive evaporation of excessive water in PVA fibers at high drawing temperature. Hot drying could remove partially the water content in PVA as‐spun fibers, thus reducing the defects caused by the rapid evaporation of water and enhancing the drawability of PVA fibers at high drawing temperature. The decreased water content also improved the orientation and crystallization structure of PVA, thus producing a corresponding enhancement in the mechanical properties of the fibers. When PVA as‐spun fibers with 5 wt % water were drawn at 180 °C, the maximum draw ratio of 11 was obtained and the corresponding tensile strength and modulus reached ～0.9 GPa and 24 GPa, respectively. Further drawing these fibers at 215 °C and thermal treating them at 220 °C for 1.5 min, drawing ratio of 16 times, tensile strength of 1.9 GPa, and modulus of 39.5 GPa were achieved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45436.     

Properties of regenerated cellulose films plasticized with α‐monoglycerides

Regenerated cellulose (RC) films were plasticized with glycerol, glycerin α‐monobutyrate, glycerin α‐monocaproate, glycerin α‐monocaprylate, and glycerin α‐monocaprate. The structure and properties of the films were investigated by using Fourier transform IR, wide‐angle X‐ray diffraction, differential scanning calorimetry, scanning electron microscopy, and tensile tests. The experimental results showed that the addition of plasticizer enhanced the elongation at break, thermal stability, and crystallinity and lowered the tensile strength of the films. The formation of hydrogen bonds between the cellulose and plasticizers weakened the inter‐ and intra‐hydrogen bonds among cellulose molecules, leading to reduced tensile strength. These α‐monoglycerides have relatively good plasticizing effects. Compared with glycerol, the resistance against water washing of the synthesized compounds was significantly enhanced. With the increase of the carbochain length of the α‐monoglycerides, the plasticizing effect decreased but the resistance against water washing was enhanced. When the RC films were immersed in a 10% glycerin α‐monocaproate solution, the elongation at break increased to 15% and stayed at 14.8% after water washing. Glycerin α‐monocaproate might be better for plasticizing RC films than others. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3500–3505, 2003     

Hydrocarbon secondary plasticizers as functional additives in flexible PVC compounds

Secondary plasticizers are additives which, by themselves, have limited compatibility with the polymer but may be used in combination with a primary plasticizer. Within the secondary plasticizers group hydrocarbon (HC) secondary plasticizers are sometimes seen as inexpensive, volatile additives that can reduce flexible PVC compound costs but that are largely lost during processing and have little plasticizing effect. However, analysis of processed flexible PVC samples shows that, depending on processing conditions and end use exposure conditions, HC secondary plasticizers can show some degree of permanence in the plastic and contribute to its flexibility. Moreover, HC secondary plasticizers can significantly improve the low temperature properties of compounds and the release of compounds from hot metal surfaces, lower plastisol viscosities, and improve plastisol viscosity stabilities. Hydrocarbon secondaries (at least the nonaromatic secondaries) have little effect on compound melt viscosities. Compatibility of some of these secondary plasticizers can be quite adequate and their effects on compound processing temperatures can be slight. J. VINYL. ADDIT. TECHNOL., 11:76–82, 2005. © 2005 Society of Plastics Engineers     

热塑性魔芋葡甘聚糖流变特性研究

以合成的魔芋葡甘聚糖(KGM)为基体,甲酰胺、乙二醇、甘油为增塑剂,碳酸钙、纳米二氧化硅、木质素为填料,通过熔融共混法制备了KGM热塑材料,并研究了温度、转速、增塑剂及填料对其流变特性的影响。结果表明:在温度150℃、转速30r/min、常压条件下,KGM热塑材料的最大扭矩为30.5N-m,平衡扭矩为10N-m,塑化时间为30s,具有较好的加工性能;增塑剂和填料可以有效降低KGM热塑材料的最大扭矩和平衡扭矩,降低生产能耗,其中甲酰胺增塑效果最好,纳米二氧化硅填充效果最优,碳酸钙最具有实用价值。     

Preparation and characterization of films based on crosslinked blends of gum acacia,polyvinylalcohol, and polyvinylpyrrolidone-iodine complex

In an attempt to develop iodine-release systems based on polymeric blend for biomedical applications, our research group prepared blends of gum acacia (GA), polyvinylalcohol (PVA), and polyvinylpyrrolidone-iodine (PVP-I) complex. The blends of GA/PVA and GA/PVA/PVP-I prepared from the aqueous solutions of the polymers were crosslinked with glutaraldehyde to increase the water resistance of the films and to improve their thermal and mechanical properties. The crosslinked GA/PVA and GA/PVA/PVP-I blend films were characterized by FTIR spectroscopy, DSC, and TGA. The swelling behavior of the prepared blends was investigated and crosslinked GA/PVA blend films were found to be pH sensitive. The properties of PVP-I containing blends differed from those prepared without it probably due to the formation of an intermolecular interaction between PVP-I and the hydroxy-polymers. The results indicated that after crosslinking the blends showed improvement in water resistance, thermal, and mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008