Modification of the fiber-matrix interface of p-aramid fibers using gas plasmas

To modify the interface between bisphenol-A epoxy and the p-aramid poly(p-phenylene terephthalamide) (PPTA, Kevlar® 49) and co-poly(p-phenylene/3,4'-diphenylether terephthalamide) (CPDT, Technora®) fibers, argon, nitrogen, and carbon dioxide gas plasmas were used. The effects on the fibers were characterized by changes in the fiber tensile strength and the interfacial shear strength; the latter was measured using the microbond test method. Inspection of the surface topography was conducted using a scanning electron microscope. It was found that the plasma treatments did not influence the tensile strength of either of the fibers. However, the results of the microbond test showed a 10-20% improvement in the interfacial shear strength for PPTA, but for CPDT the shear strength decreased by about the same amount. Examination with the scanning electron microscope showed no changes in the surface topography of either p-aramid fiber after the plasma treatment.