Surface Modification of PEEK fabric via UV Irradiation, Air Plasma, and Oxygen Plasma: Effects on Adhesion to Epoxy Resin

Poly(ether-ether-ketone) (PEEK) fabric is extensively utilized in aircraft engine noise reduction systems owing to its low nonlinear coefficient, wide operational temperature range, and superior flame-retardant characteristics. However, the insufficient adhesion strength between unmodified PEEK fabric and epoxy resin frequently leads to delamination damage, compromising noise reduction efficacy and posing a risk of device malfunction. Consequently, it is imperative to enhance the surface of PEEK to improve its adhesion with epoxy resin adhesives. In this study, PEEK fabric was subjected to modification through ultraviolet irradiation and plasma treatment, respectively. The findings indicated that both ultraviolet irradiation and plasma treatment significantly increased the concentration of oxygen-containing functional groups on the PEEK surface, thereby enhancing its hydrophilicity and the adhesion strength between PEEK and epoxy resin. However, extended treatment periods resulted in surface degradation, forming an oxidized layer with diminished mechanical properties, which ultimately reduced the adhesion strength between PEEK and epoxy resin. Notably, the cleaning-etching effects of plasma treatment effectively eliminated the degraded layer which has weak interaction force with PEEK, thereby augmenting the bonding strength between PEEK and epoxy resin. Among all the treatments, oxygen plasma treatment for 20 minutes achieved the highest adhesion strength, increasing the lap shear tensile strength from 249 to 618 kPa. This sample also attained an O/C ratio of 0.47 and a water contact angle of 0° at 10 s.