Posted on 06/09/2019 in 2019
Sulfenamide synergists for PIN FRs

Sulfenamides are organic PIN chemicals containing nitrogen-sulphur bonds and carbon rings. Five different sulfenamides were synthesised, with in some cases additional nitrogen groups, and were tested as synergists to PIN flame retardants in polypropylene (phosphonate ester, aluminium hypophosphite, AHP, ATH, APP). The N-S bond in these sulfenamides had low basicity and was stable at plastics processing temperatures. Previous publications (see Tirri, pinfa Newsletter n°74) have shown sulphonamides to be effective PIN FR synergists in polyethylene and polystyrene. In this paper, in polypropylene, 0.5% loading of sulphonamides achieved UL94-V0 (1.6 mm) with <10% total FR + synergist loading, or UL94-V2 at <5%. Peak smoke release rate occurred 3-4 times later than for neat polypropylene, resulting in lower total smoke release. Peak and total carbon monoxide release were also considerably lower. The authors conclude that radicals released by decomposition of the sulphonamides in fire improve the thermal stability of char, and that these sulphonamides have potential as PIIN flame retardant synergists.

“Sulfenamides in synergistic combination with halogen free flame retardants in polypropylene”, T. Tirri et al., Polymer Degradation and Stability 164 (2019) 75e89,

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