STRUCTURAL STUDIES ON LARGE SPHERULITES OF POLY(P-PHENYLENE TEREPHTHALAMIDE)

The poly(p-phenylene terephthalamide) (PPTA) molecule is typically rigid; and PPTA fibers have good thermal stability and ultrahigh modulus and strength. For better understanding of these interesting physical properties, structural investigations of this polyamide have been conducted by many researchers. Using microbeam x-ray diffraction and electron microscopy, the authors examine the crystal modification and molecular orientation in large PPTA spherulites after treatment with water. From the evidence obtained from scanning electron micrographs, it is shown that there is the presence of a skin and core structure. The thickness of the skin changes from 20 to 200 mu m with location. It is also found that the molecular axis of PPTA in the core part must lie along the radial direction of the spherulite (positive spherulite) rather than tangential (negative spherulite) as reported by many researchers.