Effect of Copolyamide Surface Treatment on Carbon Fiber Influencing the Interfacial Properties of Carbon Fiber and Polyamide 12

Abstract

Surface treatment of commercially available carbon fibers is not suitable for thermoplastic matrix because they are assumed to be used mainly with epoxy matrix. The interfacial shear strength between carbon fiber and PA12 is lower than that between carbon fiber and epoxy resin. For the practical use of fiber reinforced thermoplastic, it is necessary to develop a surface treatment method on carbon fibers for thermoplastic matrix. It has been reported that the mechanical properties of carbon fiber and PA66 was improved by applying polyamide resin on the surface of carbon fiber. It was reported that PA6 synthesis on carbon fibers improves the adhesion between carbon fibers and PA12, and increases the tensile strength of composites, however this method requires many procedures for chemical reactions. Therefore, it is necessary to develop a simple surface treatment method for carbon fibers. Copolyamide emulsion is a water-based emulsion mainly composed of copolyamide resin and it is a suitable surface treatment agent for carbon fibers with its excellence in adhesion, chemical and heat resistance. In this study, wettability test and single fiber pull-out test were conducted to clarify the effect of copolyamide surface treatment of carbon fiber on the interfacial properties of carbon fiber and PA12. The carbon fiber coated with copolyamide emulsion showed better wettability and higher interfacial shear strength with PA12 than that of unsized carbon fiber.