IMPROVED ADHESIVE PROPERTIES OF HIGH-MODULUS POLYETHYLENE STRUCTURES .3. AIR-PLASMA AND AMMONIA-PLASMA TREATMENT

Air- and ammonia-plasma treatments markedly improve the adhesion of ge l-spun high-modulus polyethylene (PE) tapes to epoxy resin, as measure d by pull-out and evidenced by the change in failure mode from interfa ce controlled to shear failure within the PE. By monitoring the change s in wetting, surface topography and surface composition, the factors responsible for the adhesion could be identified. These results sugges t that for air-plasma-treated PE tapes the adhesion depends on (1) the physicochemical interaction between the various carbon-oxygen functio nalities and the epoxy resin, (2) mechanical interlocking, and (3) non -polar dispersion forces. The pull-out strength is the sum of these th ree terms and their contributions in this specific system are about 76 %, 12% and 12%, respectively. Physicochemical interactions of the amin e groups, in addition to non-polar dispersion forces, determine the ad hesion of ammonia-plasma-treated PE tapes to epoxy resin. Their contri butions are 87% and 13%, respectively.