Comparative deformational characteristics of poly(styrene-b-ethylene-co-butylene-b-styrene) thermoplastic elastomers and cross-linked natural rubber

Three poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) thermoplastic elastomers (TPEs) are studied mechanically and compared to cross-linked natural rubber. It is observed that subtle alterations in the mid-block of the TPEs affect their mechanical properties significantly. The stress relaxation at room temperature is significantly altered indicating a reduced flow in systems where the ratio of ethylene to butylene segments in the mid-block is greater than one. The cyclic behavior of these systems also shows significant hysteresis. Differential scanning calorimetry suggests that these TPEs crystallize at low temperatures, similar to the observed behavior in cross-linked natural rubber. Results of internal energy changes from deformation calorimetry provide evidence for strain-induced crystallization occurring in certain SEBS systems, similar to the internal energy changes observed for cross-linked natural rubber. Simultaneous WAXD/SAXD measurements on deformed SEBS samples highlight deformation at the nanometer and the molecular length scales. In situ WAXD at different strains further reinforces the evidence for formation of strain-induced crystallites in the selected systems. Strain-induced crystallization occurring in certain TPEs provides a mechanism for reduction of flow at high strains and accounts for the retention of their highly elastic behavior.     

Structural and property changes during uniaxial drawing of ethylene-tetrafluoroethylene copolymer films as analyzed by in-situ X-ray measurements

The structure-property relationship during uniaxial drawing of high-molecular-weight ethylene-tetrafluoroethylene copolymer (ETFE) film was analyzed based on a combination of in-situ wide-angle X-ray diffraction (WAXD) and stress measurements. In-situ WAXD patterns indicated that the hexagonal (100) reflection transformed from the initial un-oriented ring into equatorial spots via split arcs at temperatures both below and above T_g, but that the critical strain when such transition occurred was delayed above T_g. Drawing above T_g produced an equatorial concentration of the spot reflections; thus, the extended chain crystal was enhanced as a result of elongation of the strain-hardening region. In contrast, the draw below T_g remained less oriented even just before breaking. However, the high orientation component also appeared beyond the critical strain; it could be assigned to the so-called “tie molecules” that bind the deformed lamellae. Changes in resultant tensile strength could be interpreted by these extended chain crystals and characteristic tie molecule components.     

计算涤纶纤维晶区取向因子中的数学问题

研究用ＰｅａｒｓｏｎⅦ函数描述涤纶纤维１０５晶面衍射强度周向分布的可行性及为准确拟合衍射线形在数据处理过程中所用的数学方法和需要注意的问题。     

固相法CPE非晶相中氯含量的WAXD法测定

本文采用迭代法对固相氯化法氯化聚乙烯(CPE)的广角X射线衍射(WAXD)数据进行处理,同时获得了固相法CPE非晶相含量和非晶相中氯含量的定量数据。实验结果表明:对于表现氯含量为2.1％～12.0％的CPE,其非晶相含量是原料PE的1.9～3.4倍,非晶相中的氨含量是表观氯含量的1.7～3.0倍。     

聚酯饮料瓶结晶与取向研究

应用广角 X射线衍射及密度法研究了聚酯饮料瓶结晶与取向及其原料和半成品的结构。结果表明 ,聚酯饮料瓶坯已有晶核生成 ,在聚酯瓶成型过程中 ,由于纵向拉伸与横向吹胀阶段拉伸张力的各向异性 ,聚酯产生了方向不同的结晶与取向作用 ,导致 PET瓶料的结晶与取向的差异。广角 X射线衍射法可以测定聚酯饮料瓶结晶与取向结构 ,可为固相缩聚 PET的聚合及吹瓶工艺提供参考。     

Analysis of surface degradation of high density polyethylene (HDPE) insulation material due to tracking

In the present work, tracking phenomena has been studied with HDPE material under a.c. voltage, with ammonium chloride as the contaminant. It is noticed that the tracking time depends on the conductivity and flow rate of the contaminant. The diffusion coefficient of the material was obtained. The thermal and chemical stability of the material were identified by carrying out a methodical experimental study. The physico-chemical analyses viz. wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), were carried out and it was concluded that the mechanism of tracking process is due to the surface degradation. The surface condition of the insulation structure was characterized for any surface discharges or tracking, using the leakage current measurement, utilizing the wavelet concepts.     

X-射线衍射测定PP/EV共混物晶胞参数的研究

用X-射线衍射法测定了PP/EVA共混物的晶胞参数,结果显示:PP/EVA共混物中基体PP的晶体为υ-晶型,属单斜晶系。PP的晶胞参数并没有由于EVA的加入而发生改变,PP和EVA没有形成共晶,PP/EVA共混物的结晶与其组成无关。     

Generation and characterization of nano aluminium powder obtained through wire explosion process

In the present study, nano aluminium particles were produced by wire explosion process (WEP) in nitrogen, argon and helium atmospheres. Thus produced nano particles were characterized through certain physico-chemical diagnostic studies using wide angle X-ray diffraction (WAXD) and by energy dispersive analysis by X-rays (EDAX). The size and shape of the powder were analysed by using transmission electron microscopic (TEM) studies. The particle size distribution studies were performed by adopting log-normal probability distribution. The relationship between size of the particle generated in the explosion process and the type of inert gas/pressure was analysed. The mechanisms of nano particle formation, the factors which can aid the process of formation of nano particle in the wire explosion process were analysed. It is realized that energy deposited to the conductor and duration of current flow have major impact on particles produced by this process.     

UHMWPE凝胶结晶膜结晶形态的小角X射线衍射研究

由准稀溶液速冷凝胶（冻胶）化结晶方法制备出超高分子量聚乙烯（ＵＨＭＷＰＥ）膜。对不同成膜浓度条件，以及再经不同温度（室温～１３０℃）热处理后所获得的膜，用小角Ｘ射线衍射方法及广角Ｘ射线衍射仪对称反射几何布置，观测了它们的片晶层积状结构及其形态的变化。结果表明，这种Ｃ轴垂直于膜面的片晶层积状形态结构与初始成膜浓度有关。发现在可达最大拉伸比的成膜浓度范围（０．４～０．５ｇ／１００ｍｌ）内，膜中片晶排列     

PET纤维结晶度测定的研究

应用 X射线衍射、差示量热、密度法对具有不同结晶和取向的 PET纤维结晶度进行了研究 ,以比较各种方法的同异与利弊。