Miscibility Studies of Poly (vinyl acetate) and Cellulose Acetate

Polymer blends of poly (vinyl acetate) (PVAc) with cellulose acetate (CA) have been prepared by solution blending, and their miscibility has been investigated by using physical techniques. Viscosity, density, and ultrasonic velocity for blend solutions at different percentages of the blend composition have been measured at 30°C. The results are discussed.     

Structural,Electrical, Mechanical,and Thermal Properties of Electrospun Poly(lactic acid)/Polyaniline Blend Fibers

Conducting electrospun fiber mats based on PLA and PAni blends were obtained with average diameter values between 87 and 1 006 nm with PAni quantities from 0 to 5.6 wt.‐%. Structural characteristics of fiber mats were compared to cast films with the same amount of PAni and studied by SEM, SAXS, and AFM. Thermal properties of fiber mats and cast films were compared by DSC analyses. Mechanical properties of fiber mats were also evaluated. It was found that electrospinning process governs the crystal structure of the fibers and strongly affects fiber properties. New properties of PLA/PAni blends are reported due to the size fiber reduction.

     

Two‐Way Reversible Shape Memory Properties of Benzoyl Peroxide Crosslinked Poly(ethylene‐co‐vinyl acetate) under Different Stress Conditions

Two‐way (reversible) chemically crosslinked semicrystalline shape memory polymers are synthesized using poly(ethylene‐co‐vinyl acetate) (PEVA) with benzoyl peroxide (BPO). The two‐way shape memory effect (2W‐SME) is achieved under both constant stress and stress‐free conditions. It is found that the stress‐free 2W‐SME can be achieved by the relationship between the initial prestretching strain (R_prestretch) and recovery strain (R_rec). Under the same prestretching stress, the stress‐free two‐way shape memory behavior can be controlled by variation of R_rec using a different setting temperature (T_set) in the recovery process. More importantly, the driving force and recovery force, as one of the key indicators for two‐way shape memory materials, are investigated, and they significantly change depending on the BPO content. The sample with high BPO content shows excellent high‐temperature creep resistant performance. A highly crosslinked structure can suppress viscous flow and provides sufficient force to allow the sample to recover its initial shape after crystal melting. Therefore, the PEVA/BPO samples are able to contract during heating. The presence of an oriented crystal structure with high applied stress that causes sample elongation during cooling is also investigated. These findings for PEVA/BPO two‐way shape memory polymers will contribute to their applications as soft actuators in various fields.     

拉伸对熔纺聚乙烯醇纤维结构形态的影响

采用含水的复合改性剂增塑聚乙烯醇(PVA),制备熔纺PVA纤维原丝。经冷拉伸3倍后,分别在160、220℃下进行热拉伸。研究了拉伸对纤维结构和表面、截面形貌的影响。结果表明:拉伸使纤维分子取向,结晶度升高;熔纺PVA纤维截面为圆形,拉伸后在纤维表面产生沿轴向的微孔,增加了纤维表面的粗糙度。     

PVAL与常用天然高分子材料复合工艺的研究进展

根据近几年国内外的公开文献,综述了聚乙烯醇(PVAL)与几种常用天然高分子材料(壳聚糖、淀粉、木质素、纤维素、海藻酸钠、大豆蛋白)复合的制备工艺,对PVAl/天然高分子材料的性能及研究应用现状进行了简要阐述,并指出了上述复合材料今后发展的方向,最后对PVAL/天然高分子材料的发展和应用进行了展望。     

Blends of poly[ethylene(vinyl acetate)] and polychloroprene: Studies on capillary and dynamic flows

Rheological properties of the blends of poly[ethylene(vinylacetate)] (EVAc; vinylacetate content 28%) and polychloroprene (CR) have been measured through capillary and dynamic uniaxial elongational flows. Capillary flow indicates their shear thinning behavior. The decrease in the out of phase viscosities with increasing frequency is in accordance with the power law equation, whereas dynamic elongational viscosities follow nonlinear relationship in log-log plot with an initial increase at 11 Hz, followed by a very sharp drop. With an increase in temperature, the viscosity for capillary flow of all blends goes down due to their positive activation energy of flow but for dynamic elongational flow of EVAc blended with CR, viscosity increases, except for 30/70 blend and pure CR, in which case the dynamic elongational viscosity decreases with an increase in temperature. This abnormal behavior in dynamic elongational viscosity is due to the process of melting and recrystallization of EVAc at low heating rate (1°C/min) beyond the melting temperature. Capillary viscosities of all blends show positive deviation from the log additive values of pure polymers. But in the case of dynamic elongational flow, all blends show positive deviation at frequencies of 3.5 and 35 Hz and at higher temperatures (80–120°C). © 1997 John Wiley & Sons, Inc.     

Influence of Carbon‐Black Nanoparticles on Poly(butylene terephthalate) Fractionated Crystallization in Bicomponent Poly(butylene terephthalate)/Poly[ethylene‐co‐(ethyl acrylate)] Blends

Summary: The crystallization of the PBT minor phase in an EEA continuous matrix has been studied by DSC and SEM. When PBT is the minor phase, PBT crystallizes at a lower temperature, as expected, near T_c,f1 = 105 °C. Introducing different CB nanoparticles into the EEA continuous phase at contents increasing from 0.02 to 5 wt.‐% leads to important modifications of the PBT crystallization. A new PBT exotherm appears at T_c,f2 = 144 °C on the addition of CB, becoming really visible at T_c,f3 = 158 °C and finally moving to T_c,n = 185 °C at high content. The areas corresponding to these new peaks were found to increase to the detriment of that of the fractionated crystallization at T_c,f1 = 105 °C. Morphological studies and interfacial tension measurements were made to understand the surprising activity of the CB. Moreover, the substitution of the EEA phase with the less polar LLDPE confirmed the importance of the strong interactions developed by EEA with CB aggregates.

Melting and recrystallization DSC curves for the PBT/EEA 60/40 blend.     

聚醚酯/聚丙烯纤维的制备及其卷曲、收缩性能研究

采用聚醚酯和聚丙烯共混熔融纺丝,经过一定拉伸松弛后得到自卷曲共混纤维。通过对卷曲性能和沸水收缩率等的测定,探讨了共混纤维的性能。结果表明:PP含量为16%,拉伸4倍的共混纤维具有较好的卷曲性能;当拉伸倍数增大时,沸水收缩率逐渐增加,但拉伸倍数为5倍时,沸水收缩率下降;随着PP含量的增加,纤维沸水收缩率逐渐降低,经紧张热定形的纤维沸水收缩率小于经松弛热定形处理的纤维。     

镍基涂膜电化学法制备聚苯胺/聚乙烯醇复合膜

报道了-种在镍基板上涂覆聚乙烯醇(PVA)膜,通过电化学法制备聚苯胺/聚乙烯醇(PANI/PVA)复合膜的方法,再将该复合膜剥离后覆于IT0导电塑料上,考察了其电致变色性.通过循环伏安和交流阻抗测试,确定了电化学法制备PANI/PVA复合膜的工艺条件.实验结果表明:当nssA/nH2so4=1∶1,激发电压为1.10～...     

Impact of hydroquinone on thermal and electrical properties of plasticized [poly(vinyl alcohol)]0.7(LiBr)0.3(H2SO4) solid acid membrane

A novel multi‐component system containing poly(vinyl alcohol), lithium bromide, sulfuric acid, ethylene carbonate and hydroquinone was prepared using a solution‐casting technique. The presence of hydroquinone as a reducing agent in the inorganic–organic membrane structure thus produced was thought to lead to enhanced thermal stability of the membrane. The activation energy for the thermal decomposition of the product samples increased with increasing hydroquinone doping. The ionic conductivities of the films were determined from AC impedance measurements in the temperature range 300–373 K. The maximum conductivity was found to be 1.75 × 10^?3 S cm^?1 for a film doped with 4 wt% hydroquinone. The results give some insight into the potential utility of the membrane as a proton‐conducting solid polymer electrolyte. Copyright © 2011 Society of Chemical Industry     

环保型钙锌复合热稳定剂与增塑剂在 PVC中的协效作用研究

将生物基增塑剂橡胶籽油基环氧脂肪酸甲酯（ERSO）与热稳定剂油脂源多聚脂肪酸基钙锌（OMFCTS）复配,以β-二酮作辅助热稳定剂,改性聚氯乙烯（PVC）,通过热老化烘箱法、刚果红法、热重分析（TGA）、热重红外联用（TGA-FTIR）分析、热重质谱联用（TGA-MS）分析、力学性能测试及动态力学性能分析（DMA）考察了改性PVC的热稳定性及力学性能,并对8个配方改性后PVC的性能进行了对比。结果表明：与DOP/CaSt₂/ZnSt₂、DOP/OMFCTS和ERSO/CaSt₂/ZnSt₂体系相比,ERSO/OMFCTS体系的热稳定性最优,力学性能较好,改性PVC的玻璃化转变温度（38.2℃）最低,拉伸断裂伸长率达265.6%;静态热稳定时间（200℃）最长（46'21"）。ERSO和OMFCTS具有良好的协同作用,二者可有效替代传统增塑剂邻苯二甲酸二辛酯（DOP）及热稳定剂硬脂酸钙锌（CaSt₂/ZnSt₂）。     

聚乳酸/玄武岩纤维复合材料的制备及性能研究

利用混杂原理,先将玄武岩纤维与聚乳酸纤维混合制成针刺毡,再与聚乳酸树脂复合,以提高树脂基体对增强体结构的渗透和结合性能。采用正交试验法,以混杂针刺毡中聚乳酸纤维含量、复合层压压力、复合层压温度为影响因素,讨论了混杂复合层压工艺对复合材料力学性能的影响。结果表明,采用混杂复合工艺有利于复合材料力学性能的改善,且混杂纤维含量在一定范围内时,复合材料的力学性能会随着混杂纤维含量的增加而线性增强,同时复合层压压力的增加也有利于复合材料力学性能的改善;采用混杂复合工艺时,复合层压温度对复合材料力学性能的影响规律不同于传统层压复合时复合层压温度对复合材料力学性能的影响,复合层压温度过高不利于复合材料力学性能的提高。     

聚乳酸荧光防伪纤维的耐酸碱性分析

选用L16(54)正交试验表,探讨了p H值、温度及处理时间三因素对聚乳酸荧光防伪纤维性能的影响。利用荧光光谱仪、荧光显微镜、纤维强度仪等测试仪器,分析了经酸碱处理的聚乳酸荧光防伪纤维的荧光性能和力学性能。方差分析结果表明:p H值、温度及处理时间对聚乳酸荧光防伪纤维的荧光强度的影响均不显著,纤维在荧光性能方面表现出良好的耐酸碱性和耐热性;聚乳酸荧光防伪纤维的力学性能受温度的影响显著,但p H值和处理时间对其影响不显著,随着温度的升高,聚乳酸荧光防伪纤维的断裂强度呈下降趋势。     

丙烯酸(酯)改性聚醋酸乙烯酯乳液的研制

采用半连续种子乳液聚合法,使用丙烯酸(AA)功能性单体和丙烯酸丁酯(BA)软单体对醋酸乙烯酯(VAc)进行了共聚改性,制备出高固含量(50.2%)的聚醋酸乙烯酯(PVAc)改性乳液。该乳液适合用于喷雾干燥法制备可再分散聚合物粉末,并且其耐水性和耐碱性等都得到了明显地改善。对影响共聚物的诸多因素进行了较为全面地考察,得出最佳的工艺条件为:AA用量为主单体质量的3%～4%,BA用量为主单体质量的5%～10%,保护胶体用量为混合单体质量的7.5%～15%,引发剂用量为混合单体质量的0.4%～0.5%,阴/非离子型复合乳化剂的质量比为1∶2～1∶3、用量为混合单体质量的2%～3%,分散剂、消泡剂和酸碱缓冲剂等助剂均为适量,加料时间为3～4h,反应温度为70～75℃。     

Synthesis and Properties of Composite Biomaterials Based on Hydroxyapatite and Poly(L-Lactide)

Composite biomaterial composed of poly(L-lactide) (PLLA) and hydroxyapatite (HA) was obtained by using the combination of solvent evaporation technique and hot pressing. HA particles in the PLLA matrix were homogeneously dispersed. A typical morphology of brittle failure with a smooth fracture surface was observed. The addition of HA particles changed significantly the appearance of the impact fracture surface to a pattern of multiple cracks. With the increasing of the amount of the HA, the bending strength of composite decreases while the bending modulus increases. The PLLA/HA composite exhibits improved cell compatibility due to the good biocompatibility of the HA particles.     

Influence of blend composition on the physical,flame retardancy,dielectric, aging,and solvent resistance properties of poly[ethylene(vinyl acetate)] and polychloroprene

Poly[ethylene(vinyl acetate)] (EVAc) has been blended with polychloroprene (CR) to develop a compound for application in the cable industry. Physical, flame retardancy, dielectric, and solvent resistance properties have been investigated for the blends. On air and brine aging, the tensile properties for 50/50 blend remains almost unchanged, though retention in tensile properties is maximum for CR in solvent aging and for EVAc in air aging. 50/50 blend shows substantially lower set and hardness compared to EVAc. The limiting oxygen index of 50/50 blend is found to be higher compared to EVAc, which indicates sufficient inflammable capability of 50/50 blend in atmospheric air. A substantially lower dielectric constant, conductivity with good physical properties, and inflammability of 50/50 blend suggests its suitability for use as a cable sheathing compound. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 551–556, 1999     

Dynamical study on the late stage of demixing in poly(methyl methacrylate) and poly(vinyl acetate) blends

A dynamical study was made on demixing of an immiscible polymer blend, whose specimens were prepared by solvent casting and had very finely phase separated structures in the initial stage of the demixing. Light scattering experiments showed the applicability of a scaling rule to the later stage of the growth of phase separation structures. The demixing can be described by a scaling theory proposed by Furukawa.     

复合酸掺杂PVA/PANI/Ag复合膜的电化学制备及性能研究

采用电化学法制备了硫酸(H2SO4)和磺基水杨酸(SSA)共掺杂的导电聚乙烯醇/聚苯胺(PVA/PANI)复合膜,采用正交设计法优化了工艺条件,研究了沉积银电流密度和时间、拉伸对复合膜电导率的影响。采用红外光谱、X射线衍射、扫描电镜对复合膜进行表征。结果表明,最佳条件下获得的PVA/PANI复合膜的电导率为22.72 S/cm;在此复合膜上以50 mA/cm2沉积2 min银可使复合膜的电导率提高到1250 S/cm;对2种复合膜进行适当的拉伸可使其电导率分别提高20.74 %和18.04 %。复合膜有一定程度的结晶,经拉伸后其结晶度有所提高。     

Studies on the properties and structure of electron‐beam crosslinked low‐density polyethylene/poly[ethylene‐co‐(vinyl acetate)] blends

Blends of low‐density polyethylene (LDPE) and poly[ethylene‐co‐(vinyl acetate)] (PEVA), crosslinked by electron‐beam (EB) radiation, formed separate crystalline lattices with a homogeneous amorphous phase. The crystallinity of the EB‐exposed samples slightly decreased, as verified by a slight reduction in the densities and melting heats and temperatures of the samples. The results obtained from both gel content and hot set tests showed that the degree of crosslinking in the amorphous regions was dependent on the dose and blend composition. The molecular weights between the crosslinks, measured from creep data, showed that an increasing PEVA content resulted in tighter network structures, thus supporting the idea that the crosslinking density at a given irradiation dose depends on the amorphous portions of the polymers. Addition of trimethylolpropane trimethacrylate as a radiation sensitizer enhanced the gel content of the neat polyethylene significantly, while the addition of an antioxidant showed the reverse effect. A significant improvement in the tensile strength of the neat PEVA samples was obtained upon EB radiation up to 210 kGy. The irradiated LDPE/PEVA blends showed improved tensile strength and elongation at break when compared to LDPE. Copyright © 2004 Society of Chemical Industry     

Synthesis and Characterization of Co Nanocomposite Based on Poly(benzimidazole-amide) Matrix and Their Behavior as Catalyst in Oxidation Reaction

2,6-Bis(5-amino-1H-benzimidazol-2-yl)pyridine was prepared and characterized by Fourier transform infrared spectroscopy, elemental analysis, ¹H-NMR, and ¹³C-NMR spectroscopic methods. Then a new poly(benzimidazole-amide) was synthesized by polymerization of the corresponding diamine and isophthalic acid. The obtained poly(benzimidazole-amide) exhibited good yield and high thermal stability. Due to the existence of benzimidazole moieties in polymer’s structure, it has the tendency to form complexes with metal ions. So, a new poly(benzimidazole-amide)/Co nanocomposite was prepared. Morphological studies revealed that metal nanoparticles were dispersed in the polymer matrix without any aggregation. poly(benzimidazole-amide)/Co nanocomposite was used as a catalyst in the oxidation of ethyl benzene to acetophenone with tert-butyl hydroperoxide.