Synthesis of phosphorus containing flame retardants and investigation flame retardant behaviour on the textile applications

Cotton fabrics have been one of the most widely used bio-based textiles all over the world. They have been widely applied in both civilian and military fields due to their excellent properties, such as hydrophilicity, air permeability, softness, comfort and so on. However, their flammability is an important weakness and badly limited the production of high performance flame retardant textile products. Many people constantly use halogen-free phosphorus compounds as flame retardants for cotton textiles. They are cheap to manufacture, are less volatile and toxic, have good thermal stability and promote char formation during the burning process. Phosphorus compounds can catalyze char formation and reduce the flammability of cotton textiles. In this study, we have synthesized two types of reactive phosphorus containing flame retardants (MKT-1 and MKT-2) that can be covalently attached to the textile surface. MKT-1 possess anhydride and acid functionality that can react with cellulose -OH functionality. Besides that, MKT-2 has silanol groups that can react with hydroxy group present on cellulose fiber. The structures of reactive flame retardants (MKT-1 and MKT-2) were characterized by 13C- and 31P NMR. Thermal properties of the cotton fabrics were investigated by thermogravimetric analysis (TGA), surface characterization was done by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy, standard test method for flammability of blankets (BS 5852) was also applied to characterize fire retardancy. It was observed that cellulose coated with 30% MKT-2 didn't burn after the propane burner was held for 20 seconds. It also produced the highest char yield (36%) at 500 oC. Furthermore, it also indicated that covalently attached flame retardant materials are durable and do not hydrolyze under washing process.