Degradational effects on bisphenol A polycarbonate extruded at high shear stresses

Bisphenol A polycarbonate was repeatedly extruded in a capillary rheometer at high, constant shear stresses (0.15–0.95 MPa) and at temperatures between 275 and 320°C. Changes in molecular weight and molecular weight distribution were determined. Polymer degradation occurred to a much larger extent during extrustion than under static conditions; a difference explained by viscous heating effects. The chain scission reaction had an activation energy of 113 kJ mol^?1 for static as well as dynamic conditions, which indicates similar degradation mechanisms in both cases. The molecular scission followed non-random kinetics.