Ultra-drawing of polystyrene by solid-state coextrusions: molecular weight dependence of properties and processing

Abstract

Solid-state coextrusion within polyethylene at 130° C has been shown to produce ultra-drawn polystyrene (PS). Six molecular weights of atactic PS of narrow molecular weight range were ultra-drawn. A strong influence of molecular weight and extrusion draw radio (EDR) on the efficiency of coextrusion was observed. The highest EDR of 27 and orientation achieved exceed values so far reported in the literature for PS. Bi-refringence reached Δ _n =−4.2×10⁻², corresponding to 44% orientation, and the efficiency of chain extension as measured by elastic recovery was almost 100 %. The results are consistent with an entanglement deformation model for PS which facilitates molecular extension and concomitant orientation. Draw deformation of markers placed on the PS films prior to co-extrusion indicate the process is an effective elongational flow. The glass transition temperature and molecular weight did not change following draw.