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 (Sb2O3) and 5% of mixtures based on Sb2O3 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, Sb2O3 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 Sb2O3 works as an effective fire retardant. Synergism of ZnS and Sb2O3 allows the possibility of replacing half of Sb2O3 by ZnS to reach equivalent fire retardancy.
The thermal degradation and the combustion behavior of glass fiber-reinforced PA 66 materials containing red phosphorus were investigated. Thermogravimetry (TG), TG coupled with FTIR, and TG coupled with mass spectroscopy were used to investigate the thermal decomposition. The flame retardant red phosphorus was investigated with respect to the decomposition kinetics and the release of volatile products. The combustion behavior was characterized using a cone calorimeter. Fire risks and fire hazards were monitored versus external heat fluxes between 30 and 75 kW/m2. Red phosphorus acts in the solid phase and its efficiency depends on the external heat flux. The use of red phosphorus results in an increased amount of residue and in a corresponding decrease in total heat release. The decrease of the mass loss rate peak results in a corresponding decrease of the peak heat release. With increasing external heat flux applied the first effect on the total heat release decreases linearly, whereas the second effect on the peak heat release expands linearly. The investigation provides insight into the mechanisms of how the fire retardant PA 66 is achieved by red phosphorus controlling the degradation kinetics. Taking into account that a decrease of the volatile products also leads to a decrease of heat production in the flame zone and that the char acts as heat transfer barrier, a reduced pyrolysis temperature is suggested as a further feedback effect.