Research advances in the functionalization of hollow plant fibers and their application as thermal insulation fillers

Resisting cold environments remains a critical challenge for human survival. Traditional cold-weather garments, however, suffer from inadequate thermal insulation, excessive weight, and limited breathability, thereby compromising comfort. Additionally, the environmental impact of petroleum-based synthetic fibers underscores the need for sustainable alternatives. This review explores the potential of hollow plant fibers, including willow catkins, as sustainable and high-performance thermal insulation fillers. It aims to address the limitations of conventional thermal insulation materials while promoting the utilization of agricultural and forestry waste. The study systematically examines the structural characteristics of hollow plant fibers, including their unique lumen morphology, pore alignment, and natural wax coatings. It also evaluates their physical and chemical properties, with a particular focus on thermal insulation, hydrophobicity, and antimicrobial performance. Current modification techniques are critically reviewed to enhance their functional properties. Results demonstrate that hollow plant fibers exhibit exceptional thermal insulation, outperforming traditional materials such as polyester and wool. Their hydrophobic wax coatings and porous structures enable efficient moisture management, and their inherent antimicrobial properties improve hygiene. Modified fibers show enhanced durability, flame resistance, and compressibility, making them viable for applications in apparel, sportswear, and medical textiles. Innovations, such as phase-change composites and aerogels, further expand their utility in dynamic thermal regulation. In conclusion, hollow plant fibers represent a sustainable and multifunctional alternative to conventional insulation materials. This work provides a foundation for advancing eco-friendly thermal insulation solutions and the high-value utilization of biomass waste.