Catalytic grafting: A new technique for polymer‐fiber composites. III. Polyethylene‐plasma‐treated KevlarTM fibers composites: Analysis of the fiber surface

Abstract

AbstractIn this article, plasma‐treated KevlarTM fiber‐polyethylene composites prepared by the catalytic grafting technique were studied. The reactive groups COOH, OH, NH2 generated on the Kevlar fiber surface by oxygen plasma treatment were used to chemically anchor Ziegler‐Natta catalyst, which was then followed by ethylene polymerization on the fiber surface. The surface structure of the Kevlar fibers, untreated or treated by oxygen plasma, catalyst grafted, or ethylene polymerized, was characterized by X‐ray photoelectron spectroscopy (XPS), attenuated total reflection (ATR), and scanning electron microscopy (SEM). The morphology, interfacial behavior, and mechanical properties of the high‐density polyethylene (HDPE) composites reinforced by either catalytic grafted or ungrafted Kevlar fibers were investigated by means of differential scanning calorimetry (DSC), polarized light optical microscopy, tensile testing, and SEM. Special attention was devoted to the tensile properties of the composites in the direction transverse to the fibers. The experimental results show that oxygen plasma treatment increases the reactive site concentration on the fiber surface significantly and that the composites reinforced by catalytically grafted Kevlar fibers exhibit higher tensile strength both parallel and transverse to the fibers. The improved interfacial adhesion is attributed to the interfacial chemical bonding established by catalytic grafting. © 1993 John Wiley & Sons, Inc.