Flame retardant textile back-coatings. Part 2. Effectiveness of phosphorus-containing flame retardants in textile back-coating formulations A Richard Horrocks, 1 * Min Y Wang, 1 Mike E Hall, 1 Femi Sunmonu 1† and John S Pearson 2 1 Bolton Institute, Bolton BL3 5AB, UK 2 University of Huddersfield, Huddersfield HD1 3DH, UK Abstract: Selected phosphorus-containing ¯ame retardants, including some intumescents, have been formulated with selected resins and applied as back-coatings to both cotton and cotton±polyester (35:65) blended fabrics. While all formulations raise the limiting oxygen index, only those based on ammonium polyphosphate and a cyclic phosphonate enable samples to pass a small-scale version of the simulated match test, BS5852: 1979, Source 1. As expected, the back-coatings containing intumescents promoted higher levels of char formation, but these did not re¯ect in their performance to the match test where most incurred failures. Thermogravimetric analysis suggests that the more effective ¯ame retardants as exempli®ed by ammonium polyphosphate, are those which liquefy by melting and/or decomposition well below 300 °C. It is proposed that this enables wetting by these products of the back face of the fabric and their diffusion to the front face where, as the temperature rises towards 300 °C, char formation occurs before ignition of surface ®bres can take place. # 2000 Society of Chemical Industry Keywords: cotton; cotton±polyester; back-coating; ¯ame retardant; phosphorus; intumescent INTRODUCTION A major requirement of any ¯ame-retardant back- coating treatment is its ability to transfer ¯ame- retardant properties to the ®bres on the front face to which an ignition source is applied. This is an essential requirement if such fabrics are to pass tests based on small ignition sources such as cigarettes and simulated match gas ¯ame de®ned in tests such as BS 5852. 1 The success of the well-established antimony±bromine systems 2 is primarily a consequence of their vapour phase activity. However, one problem associated with their use lies in the associated and claimed health and safety and environmental hazards during manufacture, application and disposal of brominated species and antimony residues. 3 As a consequence there have been mounting interests in developing non-halogen systems. In a previous study, 4 a ¯ame-retardant back-coating formulation containing decabromodiphenyl oxide (DBDPO) and antimony trioxide has been investi- gated on a cotton substrate. An optimum Br/Sb molar ratio was found to be 1.5:1 when a chlorine-containing resin was used for this speci®c system, and results were discussed within current mechanistic understanding. Subsequently, the effect of gradually reducing and eventually wholly replacing the halogen±antimony contents by the alternative ¯ame retardants in the resin-bonded formulation was carried out. The results showed that there is a possibility to incorporate other ¯ame-retardant additives, either in part or wholly replacing halogen and antimony in the back-coating system, to achieve acceptable ¯ame retardancy for cotton fabric. The most effective potential replace- ments were selected phosphorus-based commercially available retardants applied at similar levels. This current study describes a more systematic investigation of a number of phosphorus-containing species, which may function as components of, or wholly as, intumescent ¯ame retardants, in association with selected resins. These were examined on cotton and polyester±cotton fabrics to assess their potential in replacing halogen and antimony in back-coating formulations. (Received 28 October 1999; revised version received 8 February 2000; accepted 17 March 2000) * Correspondence to: A Richard Horrocks, Bolton Institute, Bolton, BL3 5AB, UK † Current address: Faculty of Science, Ahmadu Bello University, Zaria, Nigeria Contract/grant sponsor: B F Goodrich Chemicals Ltd Contract/grant sponsor: Albright and Wilson Ltd Contract/grant sponsor: Web Processing. Contract/grant sponsor: Surface Engineering LINK Secretariat. Contract/grant sponsor: Engineering and Physical Science Research Council. # 2000 Society of Chemical Industry. Polym Int 0959±8103/2000/$30.00 1079 Polymer International Polym Int 49:1079±1091 (2000)