A Novel Biodegradable Poly(Butylene Succinate-co-phosphonate) Copolyester

The application of polymer materials made our daily life more comfortable and convenient. However, it also causes serious environmental problems because they are hard to degrade in nature. Therefore, it is important to develop biodegradable polymers. Aliphatic polyesters, with outstanding biodegradability, bioabsorbability and biocompatibility, have attracted great interest of researchers in recent few decades. Comparing with other aliphatic polyesters, Poly (butanediol succinates) (PBS) has been paid much attention in recent years as the polymers have accepted mechanical properties and biodegradation. It is considered that the polymers PE and PPE will be replaced by PBS in the near future because of its applied characteristics. However, PBS cannot satisfy different requirements as materials, therefore, in this paper, the modification of PBS was successfully fulfilled by copolymerization to further enlarge its application fields.In detail, bis (2-hydroxyethyl) phenylphosphonate (BHEPP) was prepared via the reaction of ethylene glycol (EG) and phenyl phosphonic dichloride (PPD), then a novel biodegradable poly(butylene succinate-co-phosphonate) (PBPPS) copolymer was synthesized via direct polycondensation of three monomers: 1,4-butanediol (1,4-BD), succinic acid (SA) and BHEPP. The structure of PBPPS was characterized by 1H-NMR, moreover, the effect of the monomer ratio, amount of catalyst, reacting time and reacting temperature on the intrinsic viscosity of copolyesters had been discussed.A series of PBPPS with different molecular weights had been synthesized, and the effect of the molecular weight on thermal properties had been discussed. The results showed that the crystalline temperature, the degree of crystallinity and the melting enthalpy of PBPPS decreased with the increase of the molecular weight. Besides, the molecular weight had little effect on the thermal stability of copolyesters.PBPPS with different molar content of BHEPP had been synthesized, and the effect of BHEPP content on the thermal properties, crystalline properties and the crystalline structure of copolyesters had been studied. It was found that as BHEPP content increasing, the melting point, crystalline temperature and the degree of crystallinity decreased constantly, while the glass transition temperature almost remained the same. Moreover, the crystalline structure of PBPPS was the same as that of PBS. Besides, the mechanical properties, rheology properties and biodegradability of copolyesters with different BHEPP content had been discussed, and the results showed that PBPPS had better biodegradability than PBS.The flame retardancy of PBPPS had been studied in detail, and it was found that as BHEPP content increasing, the limiting oxygen index (LOI) of PBPPS increased remarkably. Considering the excellent flame retardancy of PBPPS, the PBPPS/PLA blends were synthesized to endow PLA with great flame retardancy, and the results showed LOI value of the blend increasing with the increase of PBPPS content. Moreover, on DSC curves of the blends, only one glass transition temperature was found, and the value was between that of PLA and PBPPS, which indicated that PLA and PBPPS were compatible, and the addition of 15wt% PBPPS had little effect on the thermal stability of PLA.