Interfacial interaction between poly(p‐phenylene terephthalamide) filament and nylon 6 matrix crystallized from the melt

Nylon 6 was isothermally crystallized at 483 K for 45 in the presence of poly(p‐phenylene terephthalamide) (PPTA) filament. Two kinds of traqnscrystalline zones were observed around the surface of PPTA filament by polarized optical microscopy. The two are designated as the interfacial and the intermediate zones from the surface of PPTA filament. The aggregation state of molecular chains in these zones was characterized by means of microbeam x‐ray diffraction and birefringence. The a*‐and the a‐axes of nylon 6 oriented perpendicularly to the filament surface, aligning along the radial direction in the interfacial and intermediate zones, respectively. The b‐ and c‐axes rotate around these a*‐and a‐axes. The DSC measurement revealed that nylon 6 molecules in the interfacial zone crystallized and also melted at a higher temperature, compared with those in the intermediate zone or with the usual three‐dimensional spherulite. Viscoelastic measurement clarified the fact that the interfacial zone had a restraining effect on the molecular motion of nylon 6 in the compostes with PPTA fiber. The interfacial zone is preferable for reinforcing the composite with respect to modulus.