Simultaneous enhancement of mechanical strength and flame retardancy of lyocell fiber via filling fire-resistant cellulose-based derivative

Functional materials such as fireproof fabrics or fibers usually destroy mechanical strength due to the introduction of flame retardant. In this work, ionic liquid 1,3-dimethyl imidazolium methyl phosphite, one solvent and modifier, was employed to fabricate phosphorylated cellulose. As a cellulose-based derivative, phosphorylated cellulose displayed good compatibility and dispersity in cellulose spinning which was proved by the uniform cellulose spinning dope and compact fiber structure. Owing to the special and similar structure, phosphorylated cellulose interaction with cellulose unit was conducive to enhancing mechanical strength of lyocell fiber. The flame retardant lyocell fibers (FRLF) with phosphorus content (<1 at %) exhibited excellent flame retardancy. The value of peak of heat release rate (PHRR) declined by 50.9 % compared with pure lyocell fibers (LF), as micro-combustion calorimetry measurement estimated. Meanwhile, the breaking strength of FRLF increased by 6.44 % compared with that of LF. In brief, this work balanced the flame retardancy and mechanical properties of lyocell fibers via one-step synthesizing fire retardant cellulose-based filler based on the structural similarity between matrix and flame retardant.