SURFACE MODIFICATION OF ULTRAHIGH MOLECULAR-WEIGHT POLYETHYLENE FIBERS BY PLASMA TREATMENT .2. MECHANISM OF SURFACE MODIFICATION

A detailed examination has been undertaken of the influence of surface treatment on the adhesion of ultrahigh molecular weight polyethylene (UHMW-PE) fibers to epoxy resin. XPS, SEM, FTIR-ATR, LRS, and contact-angle measurements have been used to characterize the chemical and physical changes of the fibers. The results, taken together, suggest that the adhesion depends on three factors: (i) chemical bonding effects, after plasma treatment, with the introduction of various kinds of oxygen-containing groups into the surface of the nonpolar polyethylene, which greatly improve the surface energy of the fibers; (ii) mechanical keying effects; and (iii) the nonpolar dispersion force. It is concluded that these three factors can be regarded as additive and the contributions from each of them to fiber/ resin adhesion are different and change with increasing treatment time. The optimum results are obtained when their respective contribution reaches about 60%, 30%, and 10%.