Synthesis And Biodegradability Studies Of Poly(Ethylene Succinate) Biodegradable Polyester

Poly(butylene succinate)(PBS) is a kind of biodegradable polymer materials with excellent general properties, which can be completely degraded into CO2 and H2O by microorganisms in environment. However, the production and application of the polyester is limited by its high cost at present. Poly(ethylene succinate)(PES) is, the homologue of PBS, in possession of good general properties, right thermostability and biodegradability and moreover, the rate of biodegradation is faster than that of PBS. And more importantly, the cost of raw materials of PES is lower than that of PBS. It is therefore able to reduce evidently, in some occasions, the cost of products by mixing PES with PBS or substituting PBS by PES directly. In this dissertation, we probe into the synthesis of Poly(ethylene succinate) and develop an easy synthetic process with high molecular weight poly(ethylene succinate)(PES) and short reaction time. The properties of PES obtained are characterized. Subsequently, the biodegradability of PES synthesized is estimated by biodegradation experiments.The main contents of the dissertation are summarized as follows:(1) A series of synthetic experiments are carried out by melt polycondensation of succinic acid and ethylene glycol through adjusting the molar ratio of succinic acid and ethylene glycol, altering the category and dosage of catalyzers, controlling the temperature in reaction and rate of high vacuum. High molecular weight poly(ethylene succinate)(PES) is also obtained. The result shows that, when the catalyzer is Sb2O3 (molar ratio: 3‰); the molar ratio of succinic acid and ethylene glycol is 1:1.3, and the temperature is 230℃in polycondensation reaction, it obtains the topmost molecular weight of PES synthesized (Mn=59496, Mw=109109). This is the optimum synthetic process.(2) The properties of PES obtained is characterized by 1H-NMR,FT-IR,WAXD,GPC,DSC and TG. The result indicates: poly(ethylene succinate) is a kind of crystalline polymers whose glass transition temperature(Tg) and melting temperature(Tm) is -11.5℃and 99℃respectively, and the degree of crystallinity is 33.2%. Moreover, the thermostability of PES is quite good with the temperature of its 1%weight loss(T1%) is 312.5℃, and PES has not been degraded completely until the temperature reaches to 450℃or so. This is relatively higher in aliphatic polyesters.(3) Under controlled conditions, the degradation behaviors of PES, joined in phosphate buffering solution with lipase Novozym435, is studied. The change of weight of PES films is characterized on the weight loss; the molecular weight is measured by GPC; and the morphological profile of PES films is observed by SEM. The result suggests that PES films can be biodegraded fast by lipase in vitro and the ratio of its weight loss reaches to 79.91 percent after degradation for 24 days.(4) According to the evaluation method of GB/T 19277-2003/ISO 14855:1999, the biodegradation behaviors of PES films under controlled composting conditions, has been researched. The samples are further characterized by GPC and SEM before and after the biodegradation. The consequence shows that PES films can be well biodegraded in compost under the controlled conditions; the ultimate biodegradation percentage reaches to 64.3 percent after biodegradation in compost for 45 days, which meets the standard of biodegradation percentage for biodegradable plastic in GB/T 20197-2006. Therefore, PES is a kind of biodegradable plastic.