The epoxy-polycarbonate blends cured with aliphatic amine .2. Thermal and mechanical properties mechanisms

Abstract

The transamidation reaction converts the carbonate and amine into N-aliphatic aromatic carbamate and urea, causing the equivalent of oxirane and amine nonstoichiometric in the primary cure stage. After postcure, the substitution reaction takes place and results in a more tightly crosslinked structure. Such a higher crosslinking density is responsible for higher T-g, tensile strength, and tensile modulus in the postcure stage than that in the primary and secondary cure stages. This trend is more pronounced in those PC-epoxy blends containing higher molecular weight aliphatic amine or a higher content of PC. This phenomenon is due to the difference in the fraction of amino group of aliphatic amine consumed in the transamidation. PC-epoxy/aliphatic amine blends show minor improvement in the high strain rate Izod impact tests, while toughness improvement for some blends is substantial at low strain rate tensile tests. (C) 1997 John Wiley & Sons, Inc.