Deformation behavior of nylon 6 solution-grown crystals

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Abstract
Aggregates of preoriented solution-grown crystals of nylon 6 were drawn by solid-state coextrusion both parallel and perpendicular to the initial lamellae. For the former, a solution-grown crystal mat, where the lamellae oriented parallel to the mat surface, was placed between split billet halves, and the assembly was coextruded. For the latter, a compacted crystal-powder billet, where the lamellae oriented perpendicular to the long axis, was inserted into a central hole of the predrilled billet, and the assembly was drawn by solid-state coextrusion. The deformation mechanisms for both initial lamellae orientations have been studied by wide-angle (WAXD) and small-angle x-ray scattering (SAXS). The effects of initial lamellae morphology and extrusion temperature were also studied. When the extrusion draw was made on a mat (parallel to the lamellar surface), a part of the initial lamellae were broken into smaller blocks and they rotated to make an angle to the draw axis. In these blocks, the molecular chains oriented along the draw axis. When the draw was made on a compacted billet (perpendicular to the lamellae), more complex changes in the morphology were observed at a small strain. Initially, the lamellae tended to orient with the fold surface parallel to the extrusion direction. At a higher strain, the transformation of lamellae to a fibrous structure proceeded in a manner similar to that observed for the drawing initially parallel to the lamellae surface. SAXS long period was markedly affected by extrusion draw temperature (T e). At a given extrusion draw ratio, the long period of a new fibrillar structure, calculated from the SAXS maximum on the meridian, was a unique function of T e and increased with T e, independent of the predrawn morphology with different lamellar thickness.

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