Interface-Engineered Long Glass Fiber Reinforced PA6 Composites: Multi-Scale Effects of POE-g-MAH on Structure and Properties

Achieving optimal fiber impregnation and robust interfacial adhesion is critical for long glass fiber-reinforced polyamide 6 (LGF-PA6) composites. In this study, a high-flow branched PA6 resin was synthesized to enhance impregnation efficiency. A multi-scale interfacial architecture was subsequently engineered using APTES-functionalized fibers and POE-g-MAH compatibilizer. Investigations revealed that loading POE-g-MAH established a robust organic–inorganic interface via covalent and hydrogen bonds dual-mode bonding. Nanomechanical mapping confirmed the formation of a gradient interfacial transition zone of 449 nm, which effectively induced crystallization and refined the crystalline morphology. Consequently, the 30 wt% LGF-PA6 composites achieved peak performance, featuring a tensile strength of 185 MPa and exceptional impact resistance at −40°C, alongside enhanced surface scratch resistance. These findings demonstrate that precise multi-scale interfacial tuning, spanning molecular-level bonding, interphase nanomechanics, and crystalline architecture, represents a pivotal strategy for the design of advanced structural composites targeting lightweight engineering applications. Highlights A high-flow PA6 was developed for efficient impregnation of glass fibers. Multi-scale regulation affects H-bonding, crystallinity, and mechanics. LGF-PA6 shows high strength, impact, and scratch resistance and low fiber float. Structure–interface–property link established across molecular to macro scales.