Using cone calorimeter to study thermal degradation of flexible PVC filled with zinc ferrite and Mg(OH)_2

摘要

Flame-retarded poly(vinyl chloride) (PVC) materials have been prepared by using zinc ferrite (ZnFe_2O_4 (ZFO)) combined with magnesium hydroxide (Mg(OH)_2 (MH)). The effects of these additives on the combustion and thermal degradation of PVC samples were studied using the limiting oxygen index test, the smoke density rating test, thermogravimetric-differential thermogravimetry, and the cone calorimeter test. The results showed that ZFO and MH were good synergists for improving the flame retardancy and smoke-suppressing of PVC/MH/ZFO blends. ZFO can significantly improve the maximum mass loss velocity in the first stage, and reduce the initial decomposition temperature and the decomposition range in the PVC/MH/ZFO blends. The char yield at 700 °C of flame-retarded PVC clearly decreased below theoretical values due to the cationic cracking reactions in the presence of ZFO. Furthermore, the PVC/10MH/10ZFO showed strong flame-retarding synergism since the decreased average heat release rate value. And the PVC/ 19MH/1ZFO presented a significant smoke-suppressing effect by the least average specific extinction area, peak smoke production rate, and total smoke produce. Moreover, the CO and CO_2 production was increased because of a large amount of fragment of char residue in contact air in the presence of ZFO.