A novel biodegradable phosphorus-containing copolyester with preferable flame retardancy and mechanical properties

Phosphorus-containing poly(butylene succinate-co-3-hydroxyphenylphosphinyl-propionate) (PBSH) was synthesized through esterification and melt copolycondensation of succinic acid (SA), 1,4 butanediol (BD) and 3-hydroxyphenylphosphinyl-propionic acid (HPPPA). The chemical structure of PBSH was confirmed using Fourier transform infrared spectroscopy (FTIR) and H-1 NMR spectroscopy. It is found that the addition of HPPPA can improve the initial decomposition temperatures of copolyesters. The LOI values of the PBSHs were increased from 22.0% to 35.0% and the UL-94 ratings of vertical burning were improved to V-0 with a relatively low content of phosphorus containing comonomer. Furthermore, we used melt postpolycondensation to increase the molecular weights of the copolyester and found that a copolymer with enough high molecular weight can maintain its good mechanical properties for practical applications.