Poly(styrene) samples were reprocessed in multiple cycles by a single-screw extruder. The reprocessed heat degraded samples were characterized by dynamic viscoelasticity and stress-strain measurement.
The decrease in molecular weight (Mη) for poly(styrene) with reprocessing was expressed by the product of the function of cycles number (n) of extrusion and the function of time (t) required in extrusion at a given temperature (T) in low t region. This decrease was not so large as that for poly(propylene), but larger than that for low density poly(ethylene). In poly(styrene), the scission of polymer chain is caused by heat degradation mainly at the highest molecular weight component. Young's modulus (E) obtained from stress-strain curves did not change for both the virgin, and heat degraded samples.
