Crystallization kinetics and thermal degradation behavior of low-density polyethylene blended with poly(bispropoxyphosphazene)

Low-density polyethylene (LDPE) was melt blended in a Brabender with differ ent amounts of poly(bispropoxyphosphazene) flame retardant, MFR. The crysta llization kinetics and thermal degradation behavior of the blends were inve stigated. It was found that MFR was incompatible with LDPE, where MFR parti cles dispersed in LDPE matrix with very weak interfacial bonding. In the bl ends, polyethylene crystals were still in an orthorhombic form and spheruli tic structure was observed. Under isothermal crystallization, the crystalli zation rate and crystallinity were both increased with the addition of MFR up to 20 phr, probably due to the decrease of viscosity and the increase in the number of nucleation sites. The Avrami parameter n was in the range of 2.2 to 2.7 for the blends. In thermal degradation behavior, the addition o f MFR increased the maximum-rate degradation temperature (T-max), char yiel d at 650 degrees C and the limiting oxygen index (LOI) of LDPE, indicating that MFR additive was beneficial in flame retardancy. Yet, it deteriorated the tensile mechanical properties of LDPE. (C) 2000 Elsevier Science Ltd. A ll rights reserved.