Development of High Ductility and Tensile Properties upon Two-Stage Draw of Ultrahigh Molecular Weight Poly(acrylonitrile)

Abstract

Solutions (1−5 wt %) of ultrahigh-molecular-weight atactic poly(acrylonitrile) (UHMW-PAN) in N,N‘-dimethylformamide were crystallized to gel by quenching from 100 to 0 °C. The dried gel films exhibited poor ductility on straight tensile draw. However, they were ductile on solid-state coextrusion to an extrusion draw ratio (EDR) of 8−16 (first-stage draw). Thus, the initially coextrusion drawn films were further drawn by a tensile force (second-stage draw). Drawability of the gel film was strongly influenced by several factors, including the solution concentration from which gel was made, first-stage EDR, and second-stage draw temperature. With increasing prior solution concentration, the ductility of a gel film decreased. The maximum achieved total draw ratio (DRt,max) by the two-stage draw and the uniformity of drawn products increased with first-stage EDR. Further, the ductility increased rapidly above ∼150 °C, reaching a maximum at ∼190 °C, and decreased at yet higher temperatures. A DRt,max of ∼110 wa...