ZnS as fire retardant in plasticised PVC

The flame retardant effect of zinc sulphide (ZnS) in plasticised poly(vinyl chloride) (PVC‐P) materials was investigated. PVC‐P containing different combinations of additives such as 5% ZnS, 5% of antimony oxide (Sb 2 O 3 ) and 5% of mixtures based on Sb 2 O 3 and ZnS were compared. The thermal degradation and the combustion behaviour were studied using thermogravimetry (TG), coupled with FTIR (TG–FTIR) or with mass spectroscopy (TG–MS), and a cone calorimeter, respectively. A detailed and unambiguous understanding of the decomposition and release of the pyrolysis products was obtained using both TG–MS and TG–FTIR. The influence of ZnS, Sb 2 O 3 and the corresponding mixtures on the thermal decomposition of PVC‐P was demonstrated. Synergism was observed for the combination of the two additives. The combustion behaviour (time to ignition, heat release, smoke production, mass loss, CO production) was monitored versus external heat fluxes between 30 and 75 kW m −2 with the cone calorimeter. Adding 5% of ZnS has no significant influence on the fire behaviour of PVC‐P materials beyond a dilution effect, whereas Sb 2 O 3 works as an effective fire retardant. Synergism of ZnS and Sb 2 O 3 allows the possibility of replacing half of Sb 2 O 3 by ZnS to reach equivalent fire retardancy.