Study on Thermal Properties and Crystallization Behavior of Blends of Poly(phenylene sulfide)/Poly(ether imide)

The thermal behavior of poly(phenylene sulfide) (PPS) blends with poly(ether imide) (PEI) was studied by differential scanning calorimeter (DSC). The crystallization temperature of PPS in blends shifted from 216.8°C to 226.4°C upon addition of 20–70% PEI contents. The heat of crystallization remained unchanged with less than 50% PEI in blends, whereas the heat of fusion decreased with increasing PEI content. The isothermal crystallization indicated that incorporating PEI would accelerate the crystallization rate of PPS. The activation energy of crystallization increased with addition of PEI. The equilibrium melting point of PPS/PEI blends was not changed with compositions.     

微孔注射成型PPS及其性能研究

以超临界氮气(SC N2)作为发泡剂,采用注射成型法制备了微孔化聚苯硫醚(PPS)泡沫塑料,研究了模具流道、SC N2含量、PPS熔胶量位置对微孔化PPS泡沫塑料泡孔特性、相对密度、力学性能及介电性能的影响。结果表明,随着模具流道的延长,微孔化PPS泡沫塑料的泡孔孔径逐渐变大,泡孔密度降低;SC N2含量对泡孔孔径、力学性能及介电性能影响不大,但泡孔密度随SC N2含量的增大而增大;随着PPS熔胶量位置的降低,微孔化PPS泡沫塑料的泡孔孔径增大,泡孔密度降低,力学性能及介电常数也相应逐渐降低。     

Effects of Carbon Fillers on Crystallization Properties and Thermal Conductivity of Poly(phenylene sulfide)

Differential scanning calorimetry and polarized optical microscopy methods were used to investigate the crystallization behavior and isothermal crystallization kinetics of poly(phenylene sulfide) (PPS)/carbon nanotube (CNT) and PPS/CNT/carbon fiber (CF) composites. In this article, the influences of CNT and CF on PPS crystallization behavior are explained. The thermal conductivity properties of composites were studied using the laser flash method. The results show that CNT increased crystallization temperature and rate and thermal conductivity greatly improved at 8 wt.% CNT content. In addition, the crystallization and thermal performance of PPS are significantly improved via synergistic effects of CNT and CF in the composites.     

Shear-induced crystallization of poly(phenylene sulfide)

The crystalline morphology of poly(phenylene sulfide) (PPS) isothermally crystallized from the melt under shear has been observed by polarized optical microscope (POM) equipped with a CSS450 hot-stage. The shish–kebab-like fibrillar crystal structure is formed at a higher shear rate or for a longer shear time, which is ascribed to the tight aggregation of numerous oriented nuclei in the direction of shear. The crystallization induction time of PPS decreases with the shear time, indicating that the shear accelerates the formation of stable crystal nuclei. Under shear, the increase of spherulite growth rate results from highly oriented chains. The melting behavior of shear-induced crystallized PPS performed by differential scanning calorimetry (DSC) shows multiple melting peaks. The lower melting peak corresponds to melting of imperfect crystal, and the degree of crystal perfection decreases as the shear rate increases. The higher melting peak is related to the orientation of molecular chains. These oriented molecular chains form the orientation nuclei which have higher thermal stability than the kebab-like lamellae that are developed later. A new model based on the above observation has been proposed to explain the mechanism of shish–kebab-like fibrillar crystal formation under shear flow.     

Dependence of the Avrami Exponent on Supercooling During Nonisothermal Crystallization of Poly(phenylene sulfide)

The nonisothermal crystallization behavior of poly(phenylene sulfide) (PPS) was studied by means of differential scanning calorimetry (DSC) at various cooling rates. The nonisothermal crystallization data were analyzed by the Ozawa theory. The Avrami exponent n was determined at several constant cooling rates. A notable variable trend of the Avrami exponent with the temperature was found. Within 215–238°C and 243–255°C, the Avrami exponent of PPS increases markedly with the increase of temperature, respectively, while within narrow temperature range from 238°C to 243°C, a sharp decrease of the Avrami exponent can be seen. It has been suggested that the nuclei formation and the geometry of spherulite growth in the nonisothermal crystallization of PPS are strongly affected by the temperature and correlated with the Regime Transition (the regime II→III transition for PPS).     

聚对苯硫醚、聚间苯硫醚及其共聚物的合成与表征

用硫磺、对二氯苯和间二氯苯为原料,在极性有机溶剂六甲基磷酰三胺中合成了聚对苯硫醚(p-PPS)、聚间苯硫醚(m-PPS)及其共聚物.用裂解气相色谱、红外光谱、X-射线衍射及热分析对所得聚合物的结构和热性能进行了初步研究.结果表明:p—PPS和m—PPS都是结晶性聚合物,间位结构引入到p-PSS的结构中明显地破坏了p-PPS的高度结晶性,降低了耐热性,但最大失重速率处温度却无多大变化.这一共聚改性途径可望用于改进p—PPS的刚性,提高其韧性.     

塑料注射成型新技术——微孔发泡技术的应用

主要介绍微孔发泡技术的工艺过程、应用特性及加工条件、气体条件对微孔发泡过程的影响     

超支化聚苯硫醚与线性聚苯硫醚的对比表征

以2,4-二氯苯硫酚为原料,采用一步法合成超支化聚苯硫醚。笔者运用红外光谱、拉曼光谱、荧光光谱、示差扫描量热分析、热重分析、广角X-射线衍射、溶解实验等分析手段,对超支化聚苯硫醚和线性聚苯硫醚的基本性能进行了对比。由于两者结构上的差异,使得两者表现出不同的特性。超支化聚苯硫醚具有三取代苯结构,具有很强的荧光效应、完全的不结晶、溶于有机溶剂、热降解温度低于线性聚苯硫醚约60℃等特性。广角X-射线衍射谱图也和结晶、无定型线性聚苯硫醚有很大不同。     

玻纤增强聚苯硫醚复合材料的增韧研究

针对玻纤增强聚苯硫醚材料韧性差的问题，对聚苯硫醚傲璃纤维复合体系的增韧进行了研究，考察了玻纤、改性聚合物、有机超细粒子对复合材料力学性能的影响。采用基体增韧（预增韧）与有机超细粒子增韧技术，在保持复合材料拉伸强度和模量的同时，较大地提高了冲击强度，获得了综合力学性能优异的纤维增强聚苯硫醚材料。     

热喷涂用聚苯硫醚树脂的研究

用硝酸和硫酸对聚苯硫醚（PPS）进行处理，所得产物用红外光谱和热分析手段进行了分析，结果表明，在添加硝酸的情况下室温处理6h，产物结构没有明显的改变，但在室温下使用硝酸／硫酸混合酸处理，产物中有砜基存在；在处理温度较高时，聚合物结构中不但发现了砜基结构，还出现了硝基取代基，由于化学反应的影响，处理后PPS的结晶能力显著下降，与未处理的PPS混合后进行热喷涂试验，取得了很好的效果，因而有望用于热喷涂。     

The Microcellular Injection Molding of Low-Density Polyethylene (LDPE) Composites

This paper reports the study of microcellular injection molding of low-density polyethylene- (LDPE) based composites. The effects of adding nanoclays and polymer additives in LDPE as well as rheological property of materials on the cell morphology, mechanical properties and surface properties of microcellular injection molded LDPE based composites are presented. For the microcellular injection molding process, when 3 wt% of nanoclays are added into LDPE-based polymers, the cell morphology can be significantly improved due to the nucleating effects resulting from the broad interface areas between polymer and nanoclays. Also, the addition of low melt flow LDPE into high melt flow LDPE could achieve smaller and denser bubbles in the polymer matrix than neat high melt flow LDPE.     

聚苯硫醚流变行为研究

采用高压毛细管流变仪研究了进口聚苯硫醚(PPS)树脂的流变性能,分析了剪切速率、温度对PPS树脂流变行为的影响。结果表明,PPS树脂的非牛顿指数均小于1;在低剪切速率下,PPS树脂的表观黏度对温度的依赖程度高于高剪切速率下的依赖程度;PPS树脂的黏流活化能随剪切速率的增加呈减小趋势,其结构黏度指数随温度升高而减小。     

微细发泡注塑成型工艺与微泡尺寸的关系

以数值模拟作为实验手段,工艺参数对微泡长大的影响的判断则采用田口实验方法来进行;结果得出各工艺参数对微泡尺寸的影响次序由大到小为：熔体温度、初始填充量、注射时间、模具温度。在此基础上,进一步研究了各个工艺参数对微泡长大的影响,得出适当降低熔体温度和提高初始填充量可以优化微细发泡注塑制品的微泡尺寸;而注塑时间和模具温度对微泡尺寸的影响不大。     

聚苯硫醚皮芯复合纤维的性能研究

以聚苯硫醚(PPS)树脂和聚对苯二甲酸乙二醇酯(PET)树脂为原料,采用复合纺丝技术,制得PPS-PET皮芯复合纤维。对纯PPS纤维和PPS-PET复合纤维分别进行了紫外线照射、热处理和耐酸碱处理,对比了两者处理后的力学性能变化,验证了复合纤维应用的可行性。试验结果表明:PPS-PET皮芯复合纤维的耐热性能略低于PPS纤维;而经过同等强度的紫外光辐照后,PPS-PET皮芯复合纤维的强度保持率是PPS纤维的2倍左右;在试验条件下经过酸、碱浸泡后,PPS-PET皮芯复合纤维的强度保持率与PPS纤维相比未表现出明显差异。性能研究结果表明:通过复合纺丝,PPS纤维的综合性能有所改善。     

微孔注塑成型技术研究与应用进展

从研究微孔注塑成型原理着手,分析了微孔注塑成型的工艺过程、特点以及主要影响因素,并着重研究了近些年微孔注塑成型技术的发展现状。在此基础上,对微孔注塑成型技术的发展前景进行了预测。     

微孔注塑数值模拟的正交化试验与分析

构建了微孔注塑充模过程的数学模型,并利用Moldflow Plastics Insight 6.1进行成型窗口模拟。在注射量、注射时间、熔体温度、模具温度四个工艺参数的可行区间内,分别确定三个值,构建正交化模拟试验并分别求解,利用信噪比极差法确定最优加工参数组合。结果表明:注射量是影响泡孔半径的主要因素,较高的注射量可以得到更加均匀细密的泡孔结构。     

基于数学模型的微细发泡注塑成型工艺与微泡关系的研究

研究了微细发泡注塑成型工艺中微泡长大的数学模型,建立了成型工艺和微泡尺寸之间的数学关系。在对该数学模型进行数值分析的基础上,着重研究了熔体温度、注塑时间、模具温度、初始填充量对微泡尺寸的影响。     

聚亚苯基砜的合成与表征

以环丁砜为溶剂,用4,4'-二氯二苯砜和4,4'-联苯二酚为单体,无水碳酸钾为成盐剂,甲苯为脱水剂,采用"成盐"和"缩聚"两步反应合成出了我国长期依赖进口的特种工程塑料聚亚苯基砜(PPSU),并对产物进行了纯化。对比分析和测试了自制样品和美国Solvay公司产的PPSU样品的比浓对数黏度,C、H和K元素含量,核磁共振氢谱,傅里叶变换红外光谱,激光拉曼光谱,玻璃化转变温度和热分解温度。结果表明它们具有相同的化学结构、相近的分子量和纯度,自制PPSU的玻璃化转变温度比Solvay公司产的高约5℃,热稳定性相差不大。     

Recycling of Poly(phenylene ether) Blends

The effects of postindustry recycling of polymer blends composed of poly(phenylene ether) (PPE) on the properties of the PPE blends were investigated by simulated recycling with multiple molding cycles. Two compositions with different concentrations of PPE were reprocessed with an injection‐molding machine. Mechanical, thermal, rheological, and morphological characterizations were carried out on as‐produced and reprocessed samples to examine the influence of the number of molding cycles on the two specific PPE blends. Efforts were made to determine the effect of each molding cycle on the specific properties of the two PPE blends, including the Elastic (E), modulus, stress at break, strain at break, multiaxial impact, and melt viscosity. The results are discussed in detail. The retention of the properties correlated well with the unperturbed morphology of the compositions before and after recycling, as observed by transmission electron microscopy analyses on fractured tensile samples. However, more in‐depth microanalyses are required to identify the effect of recycling on the individual components present in the studied compositions. In this study, we aimed to establish structure–property relations upon recycling using several characterization techniques. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Investigation on the Isothermal Crystallization of Poly(phenlene sulfide) by Rheology and Polarized Light Microscopy

Multiwave frequency experiments were used to determine the critical gel behavior of the crystallizing melt of poly(phenylene sulfide) (PPS), which allowed for the simultaneous measurement of the viscoelastic properties at different oscillation frequencies. Therefore it was possible to determine the apparent critical gel point because of the shorter measuring time. The resulting critical gel time was related to the crystallization kinetics during the early stages. The isothermal crystallization kinetic of PPS was calculated by rheometer and hot stage-polarized light microscopy (PLM) experiments. The Avrami exponent n from PLM and rheological techniques was 2.9 and 2.7, therefore the two methods were around 3. The half crystallization time was 2025s for optical microscopy and 2112s for the rheological techniques, and were in good agreement with each other.