THERMAL-DEGRADATION AND FIRE BEHAVIOR OF UNSATURATED POLYESTER WITH CHAIN-ENDS MODIFIED BY DICYCLOPENTADIENE

This work deals with the thermostability and the thermal behaviour of unsaturated polyester materials with dicyclopentadiene end cap (DCPD). These new UP resins will be used for naval applications, limiting sty rene emission during processing. The thermostability has been studied by thermogravimetric analysis (TGA) both in air and in nitrogen to det ermine thermal and thermooxidative mechanisms, and activation energy w as calculated for different rates of reaction. In the beginning of the rmal degradation, La was about 100 kJ mol(-1), which corresponds to po lystyrene depolymerization; for alpha=0.5, which corresponds to UP net work degradation, La was 170 kJ mol(-1); for the thermooxidation phase , Ea was about 250 kJ mol(-1). Limiting Oxygen Index (LOI) has been de termined to study fire behaviour. LOI decreases when the styrene conte nt decreases and material fire behaviour was better when the samples w ere post cured. Oxygen indexes are higher for UP modified by dicyclope ntadiene (DCPD) chain ends than for classical ones. Products formed du ring the thermal degradation have been identified using coupled pyroly sis gas chromatography mass spectrometry analysis. During thermal degr adation, water, carbon monoxide and carbon dioxide are the most import ant products; the major degradation step for UPs was ester linkage rup ture. Styrene and products derived from styrene were detected. For UP prepolymers modified by dicyclopentadiene end caps, products based on DCPD structure and on polycyclic molecules were also detected. (C) 199 8 Elsevier Science Limited. All rights reserved.