Performance and structure changes of the aromatic co-polysulfonamide fibers during thermal-oxidative aging process

摘要

The changes in performance during thermal-oxidative aging process of the aromatic co-polysulfonamide (co-PSA) fibers over a broad temperature range from 250 degrees C to 320 degrees C have been investigated. In addition, the mechanism of thermal-oxidative aging process has been studied by using structural information obtained from the fibers at varying length scales. The results showed that a significant reduction in tensile strength was observed compared with that of initial modulus during aging process. Macroscopically, thermal-oxidative aging mainly causes color changes of fibers and thermally induced macro defects begin to appear only at 320 degrees C for 100 h. On a micro level, the crystal structure of fibers remained stable and did not show significant changes expect that aging at 320 degrees C. In addition, thermo-degradation as well as crosslinking has been observed primarily in amorphous region. With the increase of temperature and time duration, the crosslinking became more dominant and crosslinking density increases. Correspondingly, the fibril length decreases due to degradation and then increases due to the formation of crosslinked structures within the fibers. The results suggest that molecular degradation is the main cause of strength loss and the formation of crosslinking structure within the fibers contributes to the retention of modulus and improvement of creep resistance. (C) 2016 Wiley Periodicals, Inc.