Improvement of the adhesion of Kevlar fiber to bismaleimide resin by surface chemical modification

Kevlar 49 fibers were surface-modified by chlorosulfonation and subsequent reaction of -SO2Cl with some reagents (allylamine, ethylenediamine, and dei onized water) to improve the adhesion to 2,2-bis[4-(4-maleimidophenoxy)phen yl]propane (BMPP) resin. The change in fiber surface morphology and the sur face functional groups introduced to the surface of the fiber were investig ated by scanning electron microscopy (SEM) and electron spectroscopy for ch emical analysis (ESCA), respectively. From the results of ESCA analysis, it was confirmed that the surface composition of the Kevlar fibers was signif icantly different from that of the bulk composition. After chlorosulfonatio n, the surface concentration of carbon was markedly decreased. The subseque nt reaction with ethylenediamine, allylamine, and deionized water also chan ged the surface composition of the fiber; e.g. treatment with ethylenediami ne and allylamine decreased the O/N ratio. On the other hand, the O/N ratio was increased by hydrolysis treatment. The synthesized 2,2-bis[4-(4-maleim idophenoxy)phenyl]propane (BMPP) resin was identified by FTIR, NMR, and dif ferential scanning calorimetry (DSC). The microbond pull-out test was then used to measure the interfacial shear strength (IFSS) between Kevlar fibers and BMPP resin. The results showed that the IFSS increased by a factor of 1.07-1.62 after chemical treatments. The fracture surfaces of fibers from m icrobond pull-out specimens were examined by SEM.