Crystalline memory on polycarbonate

Abstract

AbstractA significant reduction on the time for thermal crystallization of Bisphenol‐A polycarbonate has been achieved by means of a previous crystallization step of the polymer in acetone, followed by a capillary extrusion processing at temperatures above its melting range (230–280°C). The crystallinity of PC was corroborated qualitatively by means of WAXS and quantitatively by means of DSC. The acetone‐crystallized polymer showed higher values of dynamic viscosity than its amorphous counterpart. Such difference decreased with the increase of the test temperature and disappeared at 280°C. The degree of crystallinity of thermally crystallized PC increased with the decrease of the capillary extrusion temperature of the acetone‐crystallized material. It is inferred that the time–temperature‐dependent long range molecular diffusion necessary for the total melting of the crystal fractions could not take place entirely for the short times employed (≈ 4 min), allowing the extruded polymer to behave as a self‐nucleated material.