Thermal and mechanical properties of epoxy resins cured by aminophosphazene.

Abstract

Two types of epoxy precursors; bisphenol A and phenol novolak, were cured by two kinds of aminophosphazenes; 2, 2-diamino-4, 4, 6, 6-tetraphenoxycyclotriphosphazene (I) and hexa -(4-aminophenoxy)-cyclotriphosphazene (II). Dynamic viscoelastic measurement and thermogravimetric analysis were conducted on these epoxy resins. Compared with the bisphenol A type, the phenol novolak type of epoxy specimens exhibited higher glass transition temperature and higher weight remaining at 300-500°C. The following results were obtained for the epoxies cured by aminophosphazene: E' decreases gradually with the increase of temperature; the value of E" is high and its peak is remarkably broad; and the thermal decomposition initiates at a relatively low temperature compared with the epoxies cured by m-phenylenediamine. These results suggest that the crosslink network is not uniform. The phenol novolak type of epoxy specimen cured by curing agent II exhibits relatively higher E' above 200°C and higher weight remaining in the range of temperature 400-800°C. This type of aminophosphazene is a promising candidate as a curing agent for the heat resistant and flame retardant epoxy resin, although the processability and the uniformity of the crosslink network should be improved.