Improvement of mechanical properties, thermal stability and hydrophilicity of recycled carbon fibers

The chemical and physical interactionsbetween the reinforcement and matrix play the most important roles in improving the mechanical properties of the composite. This study demonstrates the effect of surface modification on recycled carbon fibers（rCF） leading to the improvement of their various properties such as mechanical, thermal, and hydrophilicity. The function of rCF is limited due to the surface damages which occur during the recycling process. Accordingly, they need to be modified before using them as reinforcement in the composite. The recycled carbon fibers are coated by using water-based polyurethane and silane coupling agentviathe dip-coating method. The microstructure of the coating on the surface is analyzed by scanning electron microscopy. Also, after the coating, the tensile strength and Young’s modulus of the single fiber are increased by approximately 11% and 9%, respectively. Furthermore, the thermal stability of the rCFis improved significantly which is proven by thermogravimetric analysis. The chemical attachment of the coating to the surface of the fibers is demonstrated by Fourier-transform infrared spectroscopy. The surface contact angle between the resin and the single fiber is reduced from 70° to 40° after the surface modification.