A facile strategy for in-situ polymerization of P-N network coatings for durable flame-retardant cellulose

In this study, a facile method for durable flame-retardant modification of cotton fibers by in situ polymerization of P-N macromolecular physical networks is presented. The proposed method employs an in-situ Michael addition reaction to form a durable, cross-linked phosphine oxide network coatings using trivinylphosphine oxide (TVPO) and polyethyleneimine (PEI) for flame retardant finishing within the cotton fibers. The fabrics were treated using dry and steam cross-linking methods, followed by multiple laundering cycles. SEM analysis and surface characterization verified the deposition of phosphine oxide macromolecules on the surface and inside the cellulose fibers. The finished fabrics exhibited significant improvements in flame resistance, as demonstrated VFT and LOI, which could reach up to 32.5 %. Enhanced flame retardancy and durability were further confirmed through TG and CCT, characterized by increasing residue from 7.00 % to 41.33 % and reducing THR from 11.67 MJ/m2 to 0.68 MJ/m2. Moreover, the finishing fabrics had very good wash resistance and can remain flame retardant after 50 wash cycles. Possible decomposition mechanisms of flame-retardant cotton fabrics were explored by analysis of evolved gas during decomposition through TG-FTIR. The results indicated that the proposed flame-retardant system offered an effective, formaldehyde-free solution with excellent performance.