Polyketon fiber, a newly developed super fiber, has the similar tenacity and modulus to those of the p-aramid fiber and has high strength, breaking elongation and good adhesion property with a rubber. It is expected that it can be applied to the reinforcement of the mechanical rubber goods (MRG) such as tires, hoses and protective gloves. However, usually the interfacial interaction between polyketone fiber and the polymer matrix is not strong enough, and the inclusion of the polyketone fiber could form defects in the composites to cause easy failure. Therefore, it is an essential requirement to modify fiber surfaces to improve wettability for optimizing the fiber-matrix interfacial bonding. In this study, in order to improve the adhesion between polyketone fiber and natural rubber, the surface modification by plasma treatment and primer treatment of polyketone fiber was conducted. The surface energies and composition of plasma treated polyketone fibers were characterized by dynamic contact angle analyzer and XPS (X-ray photoelectron spectroscopy), respectively and their interfacial adhesion with natural rubber was measured by a microdroplet debonding test. The surface of plasma and primer treated fibers were analyzed with SEM and AFM. Surface free energy increased dramatically by the plasma treatment and its polar component was dominant, while dispersive component was negligible. According to the XPS results, increased surface energy of fiber surface was attributed to the oxygen containing groups such as hydroxyl, carbonyl, carboxyl group. Adhesion strength of primer treated polyketone cord yarn was measured by H-test. In order to evaluate the fatigue resistance of polyketone cord yarn/rubber composite, the tension-compression fatigue test was conducted. To estimate the surface changes and adhesion properties of the primer treated polyketone cord yarn, various instrumental analysis were performed including attenuated total reflectance (ATR)-IR.
Consequently, adhesion strength of plasma and primer treated polyketone fiber with natural rubber was much higher than that of untreated fiber.