Cashmere Blended with Calcium Alginate Fibers: Eco-Friendly Improvement of Flame Retardancy and Maintenance of Hygroscopicity

As a natural fiber, cashmere is favored for its softness, finesse, and warmth. However, its poor flame-retardant properties seriously affect the safety of cashmere. Current flame-retardant treatments for cashmere tend to lead to heavy metal pollution and significantly reduce wearer comfort. In this work, natural and environmentally friendly calcium alginate fibers were blended with cashmere to obtain blended fibers. The blended fibers exhibited good hygroscopicity and softness. The incorporation of calcium alginate fibers enhanced the flame retardancy of the blends, and the LOI of the blended fibers reached 40.2 without smoldering. It was due to a stable CaO protective layer formed by Ca²⁺ during combustion and the dense carbon layer with the decomposition intermediates of cashmere, which exerted a flame-retardant effect in the condensed phase. This study provided an eco-friendly approach to producing high-quality flame-retardant cashmere products.