Abstract
Poly-p-phenylene diamine terephthalamide (PPTA) chipped fibers and fibrids can be made into insulation sheet materials by papermaking wet forming and hot calendaring operations. PPTA chipped fibers offer mechanical strength for the sheet, while PPTA fibrids act as binder. Novel PPTA fibrids and chipped fibers were investigated using SEM, a fiber quality analyzer and a fiber classifier. PPTA fibrids exhibited small sized pieces with wrinkled surfaces, uniform size and a high degree of fine fibrosis while short fiber was smooth and nearly cylindrical in shape. The effect of the fibrid to chipped fiber ratio on PPTA sheet mechanical and dielectric properties is investigated and an optimal ratio of 7:3 was determined. The pore structure and thermal stability of PPTA sheet were analyzed by mercury intrusion porosimetry and TG-DSC. The structure of PPTA sheet was similar to reinforced concrete structure; the pores were small and the bind between fibers was tight. The initial decomposition temperature and TG10% of PPTA sheet are 535°C and 560°C, respectively, indicating excellent thermal properties.