The Effect of chemical treatment on reinforcement/matrix interaction in Kevlar-fiber/bismaleimide composites

The thermal properties of all the bismaleimides have been examined by differential scanning calorimetry, thermogravimetry and thermomechanical analysis. Both 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane (BMPP) and 2,2-bis[4-(4-maleimidophenoxy)phenyl]hexafluoropropane (BMIF) showed a large processing temperature range between their melting points and initial polymerization temperature, which decreased the cross-link density of the cured resins without significant reduction in their thermal resistance. The introduction of flexible groups to BMI structure improved the interfacial shear strength of the Kevlar/bismaleimide composites measured by means of the microbond pull-out test. The results of the pull-out tests show that both BMPP and BMIF have larger interfacial shear strength values than 4, 4′-bismaleimidodiphenylmethane (BMI-DMA). The surface modification with reactive functional groups can enhance both the interlaminar shear strength and T-peel strength of the Kevlar-fiber/BMPP resin system. The ILSS was markedly improved by chlorosulfonic-acid treatment. But higher concentrations of chlorosulfonic acid and longer reaction times caused a lower ILSS. From the ILSS and T-peel strength values, it can be concluded that treatment with 0.2% chlorosulfonic acid for 150 s is the optimum chlorosulfonation condition. In this study, the chlorosulfonation/allylamine treatment produced the best ILSS and T-peel strength. The fracture surfaces of the T-peel specimens were examined by SEM.