Improving Adhesion of UHMWPE with Epoxy Matrix by Reactive Ion Etching of UHMWPE Using Ar–O ₂ Plasma and the Effects of Plasma on Adhesion at the Micro- and Macroscale

Ultrahigh molecular weight polyethylene (UHMWPE) fibers offer an excellent range of mechanical properties, but their applications in composites are limited due to their inert surface, which limits matrix wetting. This study employs reactive ion etching (RIE), using Ar-O₂ gases to significantly improve the adhesion of UHMWPE fibers (with no surface finish) and tapes with epoxy at the micro- and macrolevels. Various oxygen-bearing functionalities are observed on the surface of the fiber after plasma treatment, confirmed by FTIR. These functional groups improve links between the unsized fiber and Prime20 LV epoxy resin. Consequently, the apparent interfacial shear strength (τ_IFSS), measured by microbond testing, increases by 143%, 171%, and 181% as a result of plasma exposure for 10, 60, and 300 s, respectively, compared to untreated fibers. However, the frictional stress (τ_f) in the postdebonded region of the microbond curve remains constant and independent of plasma exposure. Short-beam shear testing of interleaved composite laminates shows a 63% increase in the ILSS, along with a change of failure mode from interfacial failure to defibrillation of the tape itself after plasma treatment, mitigating a key limitation of using this material in structural applications.