聚乙烯的多重弛豫与正电子湮没寿命谱  

Structural Multi-relaxations in Polyethylene and Positron Annihilation Lifetime

作　　者：张宪锋[1] 周先意[1] 范扬眉[1] 叶邦角[1] 翁惠民[1] 韩荣典[1] 

机构地区：[1]中国科学技术大学近代物理系,合肥230026

出　　处：《Chinese Journal of Chemical Physics》2005年第1期93-99,共7页化学物理学报（英文）

摘　　要：在143～373K用正电子湮没寿命谱(PALS)方法研究了高密度聚乙烯(HDPE)中的自由体积与温度 的关系.对实验谱分别进行了三寿命成分和四寿命成分分析,并对实验拟合结果作了微分的尝试.发现经这种方 法处理后的结果对温度变化十分灵敏,并且从四寿命分析的微分曲线可以完整地观察到HDPE在该温度区间的 三重α弛豫和表观双玻璃化转变过程,而用三寿命分析的微分曲线将难以解释这些转变.这说明对部分结晶的 聚合物而言,用四寿命拟合比三寿命拟合更符合实际的物理过程;讨论了正电子在HDPE中的湮没机制,证实正 电子在HDPE的结晶区和非晶区都可能形成电子偶素(Ps),而且正电子所处的空间大小对Ps产额有影响;最后 根据PALS实验的结果直接估算了HDPE在不同温度下的热膨胀系数.The high density polyethylene( HDPE) was studied using the positron annihilation lifetime spectroscopy (PALS) in the temperature range from 143 to 373 K. For comparison each spectrum was decomposed into three and four exponential decay components, and then for the first time it was found that the first order and second derivative of four components is more sensitive to the temperature. It can show the apparent double glass transitions and three alpha transitions of HDPE clearly, and the transition points are 175, 240, 270, 310, 350 K, respectively. Some important conclusions about the formation of positronium(Ps) were made that Ps can form in the crystalline region, the yield of Ps is affected by the space that positron exists, and so on. Moreover, the coefficient of thermal expansion of HDPE was estimated directly in terms of the results of positron lifetime spectroscopy.

关 键 词：正电子湮没寿命 高密度聚乙烯 自由体积 弛豫过程 热膨胀系数 

分 类 号：O632[理学—高分子化学]