GRAFT-COPOLYMERIZATION OF EPSILON-CAPROLACTAM ONTO KEVLAR-49 FIBER SURFACE AND PROPERTIES OF CRAFTED KEVLAR FIBER-REINFORCED COMPOSITE

The anionic graft copolymerization of E-caprolactam onto a Kevlar-49 f iber surface was carried out by using a metalation reaction in a dimet hyl sulfoxide solution of sodium hydride. The effects of reaction cond itions on the graft yield and on the tensile strength of the fiber hav e been investigated. Graft yield significantly increased with increasi ng metalation time, NaH concentration, and monomer concentration. The graft yield varied from 6 to 32% with reaction conditions. The tensile strength of the fiber depended predominantly on NaH concentration. Th e retained tensile strength was over 93% when the concentration of NaH was below 2.1 mmol/L per 0.5 g of Kevlar. The discontinuous Kevlar fi ber reinforced composites were prepared by a blending/ melt-pressing m ethod. In thermomechanical and dynamic mechanical analyses, the relaxa tion peak of grafted Kevlar fiber/Nylon 6 composite film moved to high er temperatures, compared with the original Kevlar fiber/Nylon 6 compo site film. The grafted Kevlar fiber reinforced Nylon 6 composite film exhibited mechanical properties superior to those of the original Kevl ar fiber reinforced composite film. The higher thermal and mechanical properties were due to the effect of higher interfacial interaction be tween the grafted Kevlar fiber and matrix. (C) 1997 John Wiley & Sons, Inc.