CURING, COMPATIBILITY, AND FRACTURE-TOUGHNESS FOR BLENDS OF BISMALEIMIDE AND A TETRAFUNCTIONAL EPOXY-RESIN

The curing, compatibility, and fracture toughness of blends of 4,4'-bi smaleimidodiphenylmethane (BDM)/tetraglycidyl diamino-diphenyl methane (TGDDM) were investigated. Diamino-diphenyl sulfone (DDS) was used as a curing agent. BDM alone could be both homopolymerized (at a lower t emperature) and could also undergo Michael addition reactions with the primary amine of DDS. The secondary amine of DDS did not react with B DM. However, the network produced by homopolymerization was not miscib le with that produced by the latter reactions. Curing of TGDDM with DD S took place almost at the same temperature as that of the homopolymer ization of BDM, but well below the temperature of the Michael addition reaction. When a BDM/TGDDM mixture was cured with DDS In the stoichio metric ratio, the miscibility of the cured system increased with the a mount of TGDDM. This was attributed to the fact that the network produ ced by Michael addition reactions was diminished. When DDS reacted ent irely with TGDDM, the BDM/TGDDM/DDS cure yielded only a TGDDM/DDS netw ork and a BDM homopolymerized network, which were not only miscible, b ut are also interpenetrating. The superior interpenetrated network, as indicated by the highest fracture toughness, was found at BDM/TGDDM = 40/60 weight ratio in the BDM/TGDDM/DDS curing systems.