The utility of expandable graphite as a flame retardant for PVC, plasticized with 60 phr of aphosphate ester, was investigated. Cone calorimeter results, at a radiant flux of 35 kW m-2,revealed that adding only 5 wt.% expandable graphite lowered the peak heat release rate from325 ± 11 kW m-2 to 63 ± 23 kW m-2 and the total heat release from 55 ± 11 MJ m-2 to only10.7 ± 0.3 MJ m-2. All samples containing expandable graphite ignited and burned only verybriefly before flame out. The remarkable effectiveness of the expandable graphite isattributed to an excellent match between the exfoliation onset temperature of the graphite andthe onset of decomposition of the PVC. This means that the exfoliation of the graphite formsa protective barrier layer at the right place at the right time. In addition, the simultaneousrelease of halogen species by the polymer matrix and the exfoliating graphite prevents theformation of a flammable air fuel mixture.
展开▼
