Effect of Surface Modification with Titanate Coupling Agent on Properties of Polypropylene/Vapor Grown Carbon Fiber Composites

The purpose of this study is to increase the dispersibility of vapor grown carbon fiber (VGCF) filler in a polypropylene (PP) matrices. PP/VGCF composites were fabricated by a twin screw extruder. The effect of content, surface modification on the thermal conductivity, the electrical properties, and the mechanical properties of PP composites were investigated. These results indicated that thermal conductivity, the electrical properties, and the mechanical properties increased with the content of untreated VGCF and treated VGCF. PP composites showed a ductile failure in tensile testing, similar to untreated PP. In addition, untreated VGCF were non-uniformly dispersed and aggregated in PP composites. The aggregate sizes increased when increasing VGCF content. In contrast, treating VGCF surface with a titanate coupling agent had the effect of improving the dispersibility of VGCF in composites and adhesion between VGCF and PP matrix by reducing aggregate sizes and the distance between VGCF; these improved yield strength, Young's modulus, and loss modulus. In addition, surface modification significantly improved the network structure of filler in composites, which led to increased thermal conductivity and decreased surface resistance at a high content of filler.