Mechanical interlock effect between polypropylene/carbon fiber composite generated by interfacial branched fibers

Weak interface is a limiting factor to prepare polymer composite with excellent properties. Here, we report an interfacial interlocking strategy to improve interfacial strength of polypropylene (PP)/carbon fiber (CF) by manipulating interfacial diffusion and aggregation of amide-based self-assembling nucleating agent (WBG) and studied the effect of CF surface nature on the interfacial structures. The experimental results showed that when the interfacial energy between CF and WBG became low, it was favorable that the preferential localization of WBG toward the CF surfaces from polymer matrix, leading to the laterally growth of WBG fibers and the formation of interlocking interface. Single fiber fragmentation testing proved that there was a critical size of the laterally grown WBG fibers for the interfacial improvement. Only when the size exceeded 100 μm, the interfacial interlocking was strong enough to enhance the interfacial interaction, as evidenced by the substantial increases of 97% in interfacial shear strength compared to conventional PP/CF composite.