Elastic factors controlling sorption and transport properties of polyethylene
Elastic factors controlling sorption and transport properties of polyethylene
复制标题
DOI：
10.1002/polc.5070100107
复制
发表时间：
2007-03
期刊：
影响因子：
--
通讯作者：
A. Michaels;R. W. Haussleix
中科院分区：
文献类型：
--
作者：
A. Michaels;R. W. Haussleix
通过测量吸附在聚合物中的对二甲苯的活性相对于无微晶时的假设值的增强程度，确定了具有各种热历史和机械历史的聚乙烯样品中非结晶区的常数。随着温度的升高，这种增强作用逐渐减弱，并在聚合物熔点（~ 135° C）处消失，而聚合物的结晶度在100°C以下几乎保持不变。溶剂活性增强对温度而不是结晶度的这种依赖性与以下观察结果相结合，即该行为在100°C以下是可逆的。表明晶间连接链上的张力与结晶的自由能驱动力平衡。热力学分析提供了一种计算结合在连接链中的非结晶聚合物的分数的方法。该弹性有效分数随着聚合物从熔体冷却的速率从0.25增加到0.35，并且对于高度取向的冷拉伸样品接近1。非结晶聚合物的弹性无效部分大概由链折叠、环、末端和短分子组成。
The const rainment of the noncrystalline regions in polyethylene samples with various thermal and mechanical histories has been determined from measurements of the degree to which the activity of para-xylene sorbed in the polymer is enhanced relative to its hypothetical value in the absence of crystallites. With increasing temperature, the enhancement decreases smoothly and vanishes at the polymer melting point (∼135°), while the degree of crystallinity of the polymer remains virtually constant below 100°C. This dependence of the solvent activity enhancement on temperature rather than on degree of crystallinity coupled with the observation that the behavior is reversible below 100°C. suggests that the tension on the intercrystalline tie chains is in equilibrium with the free energy driving force of crystallization. Thermodynamic analysis provides a means of calculating the fraction of the noncrystalline polymer incorporated in tie chains. This elastically effective fraction increases from 0.25 to 0.35 with the rate at which the polymer is cooled from the melt, and approaches unity for highly oriented, cold-drawn samples. The elastically ineffective fraction of the noncrystalline polymer presumably consists of chain folds, loops, ends, and short molecules.