关键词: 麻纤维, 热塑性复合材料, 阻燃, 表面改性, 力学性能

Abstract: Hemp fiber-reinforced polymer composites have received significant attention due to their environmental friendliness, low density, recyclability and biodegradability. However, the poor thermal stability and high flammability of cellulose and hemicellulose in hemp fibers have severely restricted their application in fields such as automobiles, aerospace, ships and civil buildings. This paper systematically reviews the flame-retardant mechanism and modification strategies of hemp fiber-reinforced thermoplastic composites, with a focus on analyzing the synergistic mechanism of three technical paths: surface flame-retardant treatment of hemp fibers, flame-retardant modification of the matrix, and overall flame retardancy of the composite. Through a reasonable flame-retardant ratio, the flame-retardant performance and mechanical properties of materials can be simultaneously enhanced. The development of flame-retardant strategies has evolved from the traditional single addition of flame retardants to a multi-level and multi-mechanism collaborative system. Among them, the development and application of bio-based flame retardants have attracted particular attention. These flame-retardant systems derived from renewable resources not only exert flame-retardant effects in the gas phase and condensed phase, but also take into account environmental friendliness and the maintenance of material performance. Through multiple mechanisms such as phosphorus-nitrogen synergy and silicon-based carbonization, flame retardants can form a dense protective layer on the material surface, effectively isolating heat and oxygen while suppressing the generation of toxic smoke. In the selection and application of flame retardants, priority should be given to reducing the addition amount as much as possible while ensuring the flame-retardant effect, and minimizing the impact on the comprehensive performance of composite materials to the greatest extent. Additive flame retardants are the main approach to achieving this goal. Among them, highly efficient nanoscale flame retardants, with their huge specific surface area and nanoscale effect, can achieve efficient flame retardancy by forming dense carbon layers and other means at low addition amounts, and maintain the mechanical properties of materials relatively well. The multi-component composite flame-retardant system focuses on the synergistic mechanism among different components. It enhances the overall flame-retardant efficiency through the mutual promotion of multiple stages such as gas-condensation, thereby avoiding performance loss caused by excessive use of a single component. Although their mechanisms of action are different, the former relies on physical form and size effect, while the latter depends on chemical or physical synergy. However, they both strive to achieve efficient flame-retardant effects at a relatively low addition level, which is an important direction for optimizing the overall performance balance of composite materials. In addition, a review of the relevant papers reveals that by constructing a synergistic system of flame-retardant functional layers on the fiber surface and flame-retardant modification of the matrix, the interface weakening problem caused by the introduction of flame retardants can be effectively compensated for, achieving a simultaneous improvement in flame-retardant performance and mechanical strength.

Key words: hemp fiber, thermoplastic composites, flame retardant, surface modification, interfacial strength