Characterization of thermal behavior of mixed bismaleimides for composites

Three types of bismaleimides viz., 4,4'-bismaleimido diphenyl methane (BDM), 4,4'-bismaleimido diphenyl ether (BDE) and hexa-methylene bismaleimide (HMBI) were synthesized. The thermal behavior of these bis monomers in neat and blended forms was studied by thermoanalytical techniques. All the monomer systems undergo thermal polymerization after the completion of melting. An eutectic type single lowest melting point is obtained for 60 : 40 imide formulations of BDM + HMBI and BDE + HMBI. The heat and kinetic parameters of polymerization are composition dependent and they show an increasing trend with the increase of HMBI. The thermal stability and char content decrease with the increase of hexamethylene bismaleimide whereas the thermal degradation kinetics show a reverse trend. The flexural and shear storage modulus values of the glass composite laminates made with the bismaleimides are also composition and temperature dependent. (C) 1999 Kluwer Academic Publishers.