Wetting characteristics of poly( p-phenylene terephthalamide) single fibers and their adhesion to epoxy

Abstract

the circumferential dimension of poly( p-phenylene terephthalamide) (PPTA), or Kevlar 49, single fibers and their wetting behavior and adhesion properties with an epoxy resin were evaluated. A tensiometer employing the Wilhelmy principle was described for fiber size and wetting force measurements. For the fine PPTA fibers, the fiber size could be most consistently measured by the wetting force profiling along the fiber axis in a total wetting liquid. The wetting characteristics of Kevlar 49 fibers in stepwise steady-state wetting, dynamic wetting, and multiple immersions in water and in an epoxy resin were detailed. Argon glow discharge significantly improved water wettability of the Kevlar 49 fibers but lowered their wettability in the epoxy resin. The observation on wettability in water and resin and the effects of glow discharge on wettability suggested that the polar nature of the Kevlar fiber surface may be a dominant factor in determining its wettability in these liquids. Upon argon glow discharge, the resin wettability of the Kevlar 49 fiber and the interfacial shear strength between the fiber and the epoxy were both lowered.