The effects of ionization and epoxy reaction on the surface and mechanical properties of poly( p-phenylene terephthalamide) fibres

Abstract

The effects of ionization and epoxy reactions on the bulk and surface properties of poly( p-phenylene terphthalamide) (PPTA), namely Kevlar 149, fibres were studied. When the ionized Kevlar 149 fibres were quenched in water, their tensile properties were significantly lowered with increasing ionization time. The lowered tensile strengths were attributed to the reactions between the residual sodium ions in the fibres and water, and possibly the subsequent hydrolytic chain scissions of the PPTA molecules. The tensile properties of the fibres were only slightly lowered with increasing NaH concentrations. With increasing ionization time, the epoxy reaction first significantly lowered and then began to compensate for the tensile properties of the fibres. The interfacial shear strength of the Kevlar 149 fibres with the epoxy was slightly higher and was associated with better wetting property of Kevlar 149 fibres and surface compositional differences between the two PPTA fibres. The ionization and epoxy reaction conditions employed for Kevlar 49 fibres did not affect the interfacial shear strengths with the epoxy resin. The interfacial shear strength for Kevlar 149 fibres was increased from 4.35 × 10 −3 g μm −2 for the untreated to 5.29 × 10 −3 g μm −2 for the ionized and epoxy-reacted fibres, a 22% increase.