ADHESION IMPROVEMENT OF HIGH-MODULUS POLYETHYLENE FIBERS BY SURFACE PLASMA TREATMENT - EVALUATION BY PULL-OUT TESTING

The effect of plasma treatment duration on adhesion promotion of high modulus polyethylene fiber to a polyester resin matrix has been studied. The adhesion level was evaluated using pull-out tests. The relevant parameters are the average interface shear strength and the critical embedded length. Particular attention was paid to the sample preparation and testing procedure to minimize data scatter inherent to this method due in part to structural and surface defects of the fiber. The results demonstrate that adhesion is enhanced for plasma treatment times as short as 2 s, mostly because of chemical bonding. Interfacial shear resistance gradually increases for the longer times considered, up to 10 min. In the latter case, improvement may be due to fiber surface etching and roughening, rather than chemical bonding.