QUIESCENT AND STRAIN-INDUCED CRYSTALLIZATION OF POLY(P-PHENYLENE TEREPHTHALAMIDE) FROM SULFURIC-ACID SOLUTION

In the reported experiments, quiescent and strain-induced crystallization of poly(p-phenylene terephthalamide) (PPTA) from sulfuric acid solution has been studied. Negative spherulites (SA-PPTA spherulites) are formed from hot concentrated solutions by cooling. The spherulite consists of radiating fibrous lamellae several hundred angstroms wide. The electron diffraction pattern indicates that PPTA molecules are oriented perpendicular to the long axes of the fibrous lamellae and that the left bracket 010 right bracket or left bracket 110 right bracket direction of the modification I crystal and left bracket 010 right bracket direction of the modification II crystal are parallel to the long axes of the fibrous lamellae. The width of the lamellae is much smaller than the chain length of the starting PPTA. It appears that hydrolysis of PPTA during melting crystallization determines the chain length, i. e. , the width of the fibrous lamella. Stacked, lamellar structures like ″row structures″ are formed under shear. The longer axes of the fibrous lamellae are oriented perpendicular to the shear direction. It is confirmed by electron diffraction studies that the PPTA molecules are oriented parallel to the shear direction.