Fire Behavior of Low Smoke Acidity (LSA) PVC Compounds for Electrical Cables, IV: Focus on combustion products by TGA-FTIR-GC/MS, Micro Combustion Calorimetry, and Cone Calorimeter combined with CO, CO2 sensors

This thesis compared the fire behaviour of standard PVC, low smoke acidity (LSA) PVC and halogen-free compounds for electrical cables, with a focus on their combustion products. Ten jacket, bedding and insulation compounds were characterised by MCC, TGA/FT-IR and cone calorimetry, the first two also under oxidative conditions. The LSA modification based on acid scavengers reduces acidic gas emission and also improves the quality of combustion. In cone calorimetry, the CO/CO2 mass ratio of standard PVC compounds (about 0.09, up to 0.10 for S17) is halved in the LSA compounds (about 0.045), which approach the halogen-free compounds (0.020–0.025). The effect is explained by the acid scavenger capturing HCl in the condensed phase, which hinders the gas-phase radical trapping and favours complete oxidation of CO to CO2. The LSA compounds also gave the lowest heat release in MCC, whereas ignition resistance and fire growth (FIGRA) must still be assessed compound by compound. These results refer to bench-scale tests on a completely burning specimen, which overestimate the release of toxic effluents compared with medium and large scale tests, where flame retardants limit flame spread and volatile emissions. Moreover, HCl released by PVC cables decays rapidly with distance from the fire origin. Taking these aspects together, PVC cables can be considered as safe as their halogen-free counterparts in a fire scenario, with LSA compounds offering the further advantage of a less acidic and less toxic smoke.