Reprocessable bismaleimide-diamine thermosets based on disulfide bonds

Mixtures of 4,4'-bismaleimidodiphenylmethane (BMI), 4-aminophenyl disulfide (APDS) and Jeffamine (R) ED-600 (JA, an aliphatic polyether diamine) at molar ratios of 2/1/0, 6/2/1, 4/1/1 and 6/1/2 were prepolymerized at 160 degrees C, and then hot-pressed at 190-210 degrees C to give cured products (BMI-APDS-21, BMI-APDS-JA-621, 411 and 612, respectively). Also, a cured product (BMI-APS-JA-621) of BMI, 4-aminophenyl sulfide (APS) and JA at a molar ratio of 6/2/1 was similarly prepared for comparison. The FT-IR analysis of the cured products revealed that the maleimide/amine Michael addition reaction almost completely proceeded. The glass transition temperature, thermal degradation temperature and rigidity for the cured products tended to decrease with increasing feed JA weight fraction. All the pulverized BMI-APDS-JAs were reprocessed by a hot press molding method at least three times, whereas BMI-APDS-21 was not reprocessed at all. BMI-APS-JA-621 was reprocessed only once, and its recovery rate for tensile strength was much lower than that of BMI-APDS-JA-621.