A study of the layered microstructure and electrical resistivity of an injection-molded metallic fiber-filled polymer composites

Injection molding is an important processing method for conductive fiber-filled polymer composites. The disadvantage of this approach is that the electrical resistivity of the molded part increases with processing because the fiber is easily broken down under the action of flow shear stresses. In order to effectively decrease the electrical resistivity of the molding, we investigated the layered microstructure of a molded part made from stainless steel fiber-filled polypropylene and measured the corresponding resistivity of each layer for different processing parameters. We determined the optimal injection pressure to maintain the aspect ratio of the fibers and their mass fraction in each layer. The packing pressure raised the mass fraction of fibers in each layer, but the pressure also had an obvious effect on the resistivity of the skin layer and little effect on the core layer. The transcrystallinity close to the fibers was found in the subskin layer of the part. A morphological change in transcrystallinity was observed for different processing parameters, and its effect on the resistivity was assessed.