Characterization of UHMWPE fiber/matrix adhesion by dynamic mechanical spectrometry

The tensile and dynamic mechanical properties of polystyrene and a poly(styrene-co-butyl acrylate-co-cyclohexyl methacrylate) statistical terpolymer [terpolymer] reinforced by randomly oriented, discontinuous ultra-high molecular weight polyethylene (UHMWPE) fibers are presented in terms of the fiber/matrix interfacial properties. Using a thermomechanical block model based on the parallel rule of mixtures, the adhesion characteristics of poly(butyl acrylate) (PEA) and poly(cyclohexyl methacrylate) (PCHM) grafted, plasma treated, and untreated fibers were determined. The model successfully predicts the tan delta response of the composites including peak height variations and the development of additional loss dispersions associated with the interphase. Moreover, the model yields a fiber reinforcement efficiency factor, K, which gives a quantitative measure of adhesion. The contact angle of PEA and PCHM grafted high density polyethylene (HDPE) films are also included and are compared to the contact angle of plasma treated fibers, The results indicate that PEA and PCHM grafts enhance adhesion through polymer graft/matrix interactions, not simply by improved wetting.