Enhanced Interfacial Strength of Natural Fiber/Polypropylene Composite with Mechanical-Interlocking Interface

The interface, as the weakest point of a polymer composite, determines the comprehensive performance, especially in a polarity/nonpolarity system featuring poor interfacial adhesion. Here, we report an interfacial manipulation strategy to trigger the preferential adsorption of amide-based self-assembling compounds (NAs) from polypropylene (PP) melts onto the surface of natural fiber (NF) as a result of hydrogen bonding and then promote the epitaxial growth, into root-like NF fiber with interfacial interlocking effects. The unique interface constructed by the grown NA fibers rendered the PP/NF composite with strong interfacial adhesion. The substantial increases of 64.4%, 77.9%, and 94.4% in interfacial shear strength, interfacial friction, and debonding energy are achieved, respectively, in comparison to conventional NF/PP composite. Finally, the working principle of the laterally grown NA fibers on the interfacial enhancement was established based on the fracture morphology after the microbond test. This study can effectively solve the interfacial problems of a polymer composite featuring limited interfacial adhesion, via simple one-step physical blending, without any preliminary surface treatment or soft compatibilizers.