Effect of structure on thermal behaviour of phosphorus containing additionpolyimides and epoxy resins

Addition polyimides, [e.g. endo-5-norbornene-2.3-dicarboximide(nadimides), maleimides etc.] and epoxy resins have been used extensively in the past as matrix resins for advanced fiber-reinforced composites. However, inadequat e flame resistance and thermal stability of these resins is one of their se rious limitations. Our earlier studies have shown excellent flame resistanc e properties of addition polyimides based on bis(3-aminophenyl) methyl phos phine oxide (B) or tris(3-aminophenyl) phosphine oxide (T). Carbon fiber re inforced composites based on such matrix resin did not burn even in pure ox ygen. In order to investigate the effect of weight percent of phosphorus on thermal behaviour and flame resistance, a series of addition polyimides an d epoxy res ins were prepared using B, T and amide-amines. The effect of st ructure on curing behaviour of resins and thermal and flame resistance of c ured resins was evaluated. The results demonstrate an improvement in char y ield of resins containing higher weight percent of phosphorus.