FLAME RETARDANCY MECHANISMS AND PERFORMANCE OF A HALOGEN-FREE PHOSPHORUS POLYESTER IN PBT

摘要

PET-P-DOPO is a phosphorus-containing polyester prepared from the glycol ether of the hydroquinone derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and dimethyl terephthalate. PET-P-DOPO and a blend of PBT with PET-P-DOPO were investigated with respect to pyrolysis and fire behavior. PET-P-DOPO achieves a V-0 rating in the UL 94 test and exhibits a high LOI of 39.3%. The outstanding flame-retardant properties of PET-P-DOPO are the result of three different mechanisms (flame inhibition, charring and a protection effect of the intumescent char) that are active in PET-P-DOPO. The fire load and the peak of heat release rate (pHRR) are reduced to 34% and 17%, respectively. The char exhibits an intumescent multicellular structure enabling it to act as an efficient protection layer. As PET-P-DOPO is immiscible with PBT, the blend shows a lower breaking elongation than pure PBT. Compared to pure PET-P-DOPO, the flame retardancy of the blend is decreased according to the fraction of PET-P-DOPO used. Nevertheless, the flame-retardancy of PET-P-DOPO in the blend was good enough to compete with PBT flame-retarded by AlPi-Et (aluminum diethylphosphinate) that was used as a benchmark.