文献类型：期刊文献

英文题名：Expanded polytetrafluoroethylene as an auxetic material: effect of extension ratio on its structure and properties

作者：Xu, Chao[1];Tu, Yonghui[1];Yu, Ruobing[1];Yang, Xue[2]

机构：[1]East China Univ Sci & Technol, Sch Mat Sci & Engn, Shanghai 200237, Peoples R China;[2]Naval Univ Engn, Inst Noise & Vibrat, Wuhan 430033, Hubei, Peoples R China

年份：2018

卷号：27

期号：1

起止页码：49

外文期刊名：IRANIAN POLYMER JOURNAL

收录：;EI(收录号：20180104611703);WOS:【SCI-EXPANDED(收录号:WOS:000427992500006)】；

基金：This work was supported by the National Natural Science Foundation of China (Grant no. 51003209).

语种：英文

外文关键词：Extension ratio; Polytetrafluoroethylene; Negative Poisson's ratio; Damping factor; Carbonyl iron powder (CIP)

摘要：The effect of extension ratio on the structure and property of expanded polytetrafluoroethylene (ePTFE) has been decisively studied. ePTFE is unique with its porous fibrillar network structure connected by nodes and also with its degree of orientation which increases with increases in extension ratio. It is found that the Poisson's ratio of ePTFE is negative, and it is reduced dramatically with increased extension ratio. At the extension ratio of 30, the Poisson's ratio reaches - 10.00. By changes of extension ratio from 1 to 10, the segmental mobility of polymer chains becomes harder, and the dynamic glass transition temperature (T-g) is increased. Broad glass transition regions are revealed in tan delta versus temperature curves in polytetrafluoroethylene specimens stretched 20-(S20) and 30-fold (S30). As the extension ratio is increased, the thermal conductivity of the specimens is decreased. The thermal conductivity coefficient is dropped to 0.051 W m(-1) K owing to the appearance of more pores and low degree of crystallinity at higher extension ratio. The properties of ePTFE modified by carbonyl iron powder (CIP) have been investigated. CIP has affected the structure and properties of modified ePTFE. CIP-modified ePTFE also exhibits a negative Poisson's ratio which is larger than ePTFE at the same extension ratio. The modified ePTFE reveals higher thermal conductivity coefficient than ePTFE itself.