Abstract
Low density poly(ethylene) (LDPE) samples were reprocessed in multiple cycles by a single-screw extruder. The reprocessed heat degraded samples were characterized by gel permeation chromatogram (GPC), dynamic viscoelasticity and stress-strain measurement.
The decrease in molecular weight (Mw) obtained from GPC measurement for LDPE with reprocessing was small than that for poly(propylene) (PP) and poly(styrene) (PS) in the region of low degradation time (t<30 min). Degradation time dependence of the molecular weight (Mη) obtained from measurements of viscoelasticity for LDPE was very different from that for PP and PS. In LDPE, not only the scission of polymer chain but the formation of branched and crosslinked chain are caused by heat degradation mainly at the week point on polymer chain, so that Mη was constant regardless of t. Young’s modulus (E) obtained from stress-strain curves did not change for both the virgin and heat degraded samples.
