Synthesis and application of a formaldehyde-free flame retardant for bamboo viscose fabric

A formaldehyde-free flame retardant (EFFR) for bamboo viscose fabric was synthesized by raw materials of silanol, phosphorus pentoxide, and diethanolamine. The flame retardant had the dual function of imparting fire resistance and softness to bamboo viscose fabric; moreover, it had no halogen and free formaldehyde, and wouldn’t release formaldehyde during processing and end-use. The experimental results about choice of cross-linker stated that the cross-linker played a significant role in decreasing the flammability of bamboo viscose fabrics and improving durability of flame retardance. Cross-linkers of hexamethylol melamine (HMM) or dimethylol dihydroxy ethylene urea (DMDHEU) or water-soluble isocyanate-terminated (WIT) not only cross-linked with flame retardant and bamboo viscose cellulose to enhance durability of inflaming retarding, but also had nitrogen to improve nitrogen–phosphorus synergism. However, HMM and DMDHEU can release free formaldehyde. WIT is a kind of cross-linker which has no formaldehyde. The experimental results showed that the Limiting Oxygen Index (LOI) value of Vis-EFFR–WIT treated fabric was basically above 30%, and the handle of the finished fabric was ameliorated greatly because of its organosilyl constituent part, even after 30 laundry cycles, the fabric still had some flame retardancy and soft feeling.