Adhesive characteristics of alder-ene adduct of diallyl bisphenol A novolac and bisphenol A bismaleimide

Diallyl bisphenol A-formaldehyde copolymer (ABPF) was addition cured with b isphenol A bismaleimide (BMIP) making use of the Alder-ene reaction at high temperatures. The lap shear strength (LSS) of the system was found to depe nd on the conditions of cure and the stoichiometry of the reactants. Modera te cross linking achieved at a 1:1 maleimide:allylphenol stoichiometry and a stepwise cure, up to a maximum of 250 degreesC for 2 h, was found to be t he most effective in achieving the optimum LSS properties. The system exhib ited greater than 100% retention of the LSS at temperatures up to 250 degre esC. Matrix modification using polysulfone (PS) and polycarbonate (PC) resu lted in a remarkable improvement in the adhesive characteristics, although the high-temperature retention was marginally adversely affected. The perfo rmance advantage both at room temperature (RT) and at high temperature was greater in the case of PS modification, showing an optimum improvement at 2 0% loading as against PC modification, exhibiting maximum properties at 10% loading. Scanning electron microscopy (SEM) analysis confirmed that the fi ne dispersion of PS, rather than large size nodules found in PC, was conduc ive for the better performance of the former. Dynamic mechanical analysis ( DMA) corroborated the observations made in SEM. The existence of co-continu ous phases of thermoplastic, matrix and thermoplastic-dissolved matrix was evidenced in the PS modification and a clear phase separation was evident i n the case of the PC modified system, manifesting independent glass transit ions by the individual phases.