The relationship between structure and thermal property of two bisphenol A-derived polyphosphates

Abstract

To overcome the disadvantage of liquid-phase flame retardant bisphenol A bis(diphenyl phosphate) (BDP) on processing and handling, two bisphenol A-derived solid polyphosphates, poly-phenoxyl bisphenol A phosphate (S-BDP) and poly-p-tolyl phenoxyl bisphenol A phosphate (PTPBP), were designed and synthesized from bisphenol A and dichlorophosphate by melting polymerization. PTPBP was different from S-BDP in a side-chain methyl group. The structures of polymers were characterized with FTIR, 1H-, 13C- and 31P-NMR. The molecular weight was determined by GPC. Thermal stabilities of polymers were studied by TGA. The results show that both polymers present good thermal properties. PTPBP is more stable than S-BDP at the beginning of decomposition, whereas at higher temperature the latter behaves better than the former. Furthermore, PTPBP gives more residue than S-BDP at the end of decomposition. It can, therefore, be concluded that thermal properties and char yield of compounds could be improved by increasing molecular weight and side-chain substituent. This knowledge will be helpful to design novel flame retardant. Polyphosphate flame retardant can be prepared by simple melting polymerization. A side-chain methyl group will influence molecular weight and thermal stability of polymer. The phosphates represent good thermal stability under low-heat environment and maintain their structure up to 300 °C in this study.