Super Tough High-Flow Nylon Composites With Nylon Fiber-Reinforcement

High-melt-flow nylon 6 (HMF-PA6) offers excellent processability but suffers from poor interfacial bonding with reinforcements, reduced mechanical strength, and limited toughness, restricting its use in high-performance composites. In this study, nylon 66 (PA66) fiber cloth was employed as a homologous reinforcing skeleton, and its surface was modified with polydopamine (PDA) to enhance interfacial compatibility. PDA was deposited via oxidative self-polymerization, forming a thin coating that increased fiber surface roughness and introduced active functional groups capable of hydrogen bonding with the matrix. During hot pressing, the high fluidity of HMF-PA6 enabled the PDA-coated fibers to form a “mechanical interlocking” interface, thereby promoting efficient stress transfer and energy dissipation. As a result, the PDA-PA66/PA6 composites exhibited remarkable improvements in mechanical performance: tensile strength increased by 96% compared with pure HMF-PA6 and by 19% over unmodified PA66/PA6 composites, while elongation at break was enhanced by approximately 41%. Morphological observations confirmed that PDA improved fiber–matrix adhesion, and thermal analysis indicated enhanced stability despite partial PDA decomposition at high processing temperatures. These findings demonstrate a simple and scalable strategy to simultaneously reinforce and toughen HMF-PA6, highlighting the potential of PDA-modified homologous reinforcements for next-generation high-performance nylon-based composites. Summary The tensile strength of matrix nylon is greatly improved by reinforcing fibers. An effective “mechanical interlocking” structure is formed at the interface.