Phosphorus-containing poly(trimethylene terephthalate) derived from 2-(6-oxido-6H-dibenz〈c,e〉〈1,2〉oxaphosphorin-6-yl)-1,4-hydroxyethoxy phenylene: Synthesis, thermal degradation, combustion and pyrolysis behavior

A novel phosphorus-containing poly(trimethylene terephthalate) (PTT) derived from 2-(6-oxido-6H-dibenz〈c,e〉〈1,2〉oxaphosphorin-6-yl)-1,4-hydroxyethoxy phenylene was synthesized via solid state polymerization, and its chemical structure was confirmed with 1H NMR. The thermal stability of the resulting copolyester was analyzed by thermogravimetric analysis. With the introduction of phosphorus-containing segments, polyester onset weight-loss temperatures in both nitrogen and air are enhanced. Thermal degradation kinetics were analyzed using the Flynn–Wall–Ozawa method, which showed a decreased activation energy for the copolyester compared with that for neat PTT, strongly suggesting that the increased onset weight-loss temperature in nitrogen is a result of enhanced carbonization. Microscale combustion calorimetry was carried out to test the flammability behavior of the copolyester; improved flame-retardant properties were observed with incorporated phosphorus components. Py-GC–MS testing revealed that the pyrolysis of phosphorus-containing copolyester is not significantly affected by the phosphorus incorporation.