A range of sulfenamide molecules containing sulphur and nitrogen, including oligomers and polymers, were synthesised and tested as flame retardants in polypropylene PP, low density polyethylene (LDPE) and polystyrene.
Sulfenamides contain a bond of divalent sulphur and trivalent nitrogen. Their flame retardant effect is thought to result from radicals released by cleavage of S-N or S-N-S bonds which react with polymer pyrolysis products. Sulfenamide polymers have been proposed as biodegradable polymers for medical applications, and have been tested showing very low or no toxicity, suggesting that they would show a positive health and environmental profile as PIN flame retardants. For polypropylene and LDPE films, DIN 4102 B2 (self-extinguishing) was achieved at low sulfenamide loadings (0.5%). For polystyrene, UL94 V-0 was achieved at 5% sulfenamide loading.
“Structure–Property Studies on a New Family of Halogen Free Flame Retardants Based on Sulfenamide and Related Structures”, T. Tirri et al. Polymers 2016, 8, 360; http://dx.doi.org/10.3390/polym810036