Mechanical and Electrical Properties of Vapor Grown Carbon Fiber/Polypropylene Composites Made by Injection Molding

Abstract

We made pellets by adding 0-20 wt% vapor grown carbon fiber (VGCF) to polypropylene and made an injection molding test piece with the pellets so as to test the rheological, as well as the mechanical, electrical, and injection molding properties. In the test piece made by injection molding, the quantity of VGCF in the surface layer is extremely small as compared to the quantity of addition. The value of resistance at the end of flow of the injection-molded product is smaller than that measured at other locations, which is considered to be the influence of the fountain flow at the end of flow. In addition, it is known that the above phenomenon is attributable to the fact that the orientation is in the direction of thickness in the same way as the orientation of glass fiber and carbon fiber. Even if the additive rate of VGCF is the same, the value of resistance changes substantially depending on the thickness of injection-molded products. One of the causes is considered to be the orientation of VGCF, and the orientation of VGCF in the test piece is considered to be strong in the direction of flow. There exists a proportionality relation between the shear rate and the value of resistance calculated on the basis of the rate of flow, which is one of the molding conditions.