Intumescent flame retardant properties of graft co-polymerized vinyl monomers onto cotton fabric

In this work, aiming at providing flame retardant properties to cotton fabrics, a novel approach based on graft-copolymerization of vinyl monomers, containing P and N, onto cotton fabrics was investigated. The grafting reaction was carried out in presence of potassium persulfate (KPS) used as radical-initiator. The basic mechanism starts from the creation of free radical sites on both the used vinyl monomers and on cellulosic chains, in order to obtain a permanent combination of vinylphosphonic acid (VPA) and methacrylamide (MAA) with the textile substrate. As a consequence of grafting process, covalent bonds are formed between monomers and polymer, hence providing new functionalities to the treated fabric with high durability. With this goal, VPA and methacrylamide MAA)were chosen as phosphorus and nitrogen sources, respectively. Thermogravimetric analyses, performed both in air and in nitrogen atmosphere, demonstrated the anticipation of the cellulose decomposition due to the presence of the intumescent coating that allows the dehydration of cellulose, and upon decomposition, limits the production of volatile species, favoring the formation of the protective char (confirmed by the final residue). The protection feature was also confirmed by cone calorimetry tests that also highlighted the washing resistance of the coating. According to these results, horizontal flame spread tests showed for the treated samples, either before or after washing, self-extinguishing properties