Novel Flame-Retardant and Antidripping Branched Polyesters Prepared via Phosphorus-Containing Ionic Monomer as End-Capping Agent

A series of novel branched polyester-based ionomers were synthesized with trihydroxy ethyl esters of trimethyl-1,3,5-benzentricarboxylate (as branching agent) and sodium salt of 2-hydroxyethyl 3-(phenylphosphinyl)propionate (SHPPP, as end-capping agent) by melt polycondensation. The chemical structures of the branched polyester-based ionomers were confirmed with H-1 and P-31 NMR spectra. The effects of branching and ionic end groups on the melt behavior and thermal properties were investigated by differential scanning calorimetry and thennogravimetric analysis. The flammability and fire behavior were characterized by limiting oxygen index (LOI) and cone calorimeter. The LOI values of branched poly(ethylene terephthalate)s (PETs) are higher than that of pure PET. The cone calorimeter parameters of the samples such as heat release rate, total heat release, and time to ignition indicate that the fire safety of branched polyester-based ionomers is improved by introducing SHPPP. The effects of SHPPP on accelerating char forming and antidripping could be observed clearly from the pictures of the samples after LOI test.