EFFECT OF GAMMA-RADIATION-GRAFTED ARAMID CHOPPED FIBERS AS THE REINFORCING FILLER IN STYRENE-BUTADIENE RUBBER MIXTURES

Poly(p-phenylene-terephthalamide) PPTA chopped fibers, known as Kevlar 49 and related to aramid fibers, were subjected to graft copolymeriza tion with styrene under the effect of gamma radiation. The effects of different parameters includng irradiation dose, type of solvent and mo nomer concentration on the graft yield were studied. The surface-modif ied chopped fibers were introduced in styrene-butadiene rubber (SEX) m ixtures. The properties of rubber mixtures and their corresponding vul canizates were markedly affected depending on the fiber concentration. Grafting of styrene on to chopped PPTA fibers improves the mechanical properties of SBR-PPTA composites, especially in the presence of addi tional crosslining systems based on benzoyl peroxide EDMA (ethylene di methacrylate) system. (C) 1997 by John Wiley & Sons, Ltd.