Effects of uniaxial drawing on the performance and structure of filled polytetrafluoroethylene

Abstract

Based on the phenomenon of softening under drawing, the filled polytetrafluoroethylene (PTFE) composites were studied. Short glass fibers (SGFs) were added into PTFE and drew at room temperature uniaxially in different draw strain ratios. As the result showed, porosity and tension strength increased, whereas the hardness decreased during orientation. Tensile softening provided an opportunity for taking the composite as gasket material. It could be detected from the tests of compressibility and recovery that both compressibility and resiliency were improved with the increasing draw ratio, and when draw strain ratio reached 80%, resiliency was nearly three times as the nondrawn one. There were two phenomena in the filled composite: first, SGFs were debonded from PTFE resin and second, small voids and fibrils were formed, which brought unique properties such as softening and high strength to the composite. It was also found that crystals divided into smaller ones and after that rearranged at an early stage of tension. When the draw ratio reached 35%, degree of crystallinity started to increase and fibrils began to be formed. It was believed that fibrils were imperfect crystal, and kept increasing the draw ratio, fibrils grew and crystalline grain became smaller gradually. POLYM. ENG. SCI., 54:1427–1435, 2014. © 2013 Society of Plastics Engineers