Study On Modification And Properties Of Biodegradable Aliphatic Polyesters

In recent years, the biodegradable materials used in packing, pesticide, medicine and other fields have received more and more attention. It is due to that the biodegradable materials had excellent performance, which not only making our life convenient and comfortable, but also solve the environmental pollution. Withing special ester bonds which was easier to be hydrolyzed, were susceptible to break the bond in natural environment and in biosome, the biodegradable aliphatic polyester materials had becoming the hot off the press of the environment friendly materials in the world. Many biodegradable aliphatic polyester materials had been commercialized because of their excellent performance and wide application. For example, polybutylene succinate (PBS) and poly lactic acid (PLA) had been widely used in packaging, medicine and other fields. However, due to the reasons of melting point, the degree of crystallinity, their processing performance and thermal stability were difficult to content all kinds of need in the production and life filed. Therefore, we should use copolymerization and chain extension methods to achievement the aim of improving the thermodynamic and the degradation properties of polyesters. Main points and results were as follows:In the chapter1, we summarized the current status as well as the development tendency of biodegradable materials and biological degradation in resent years.In the chapter2, we introduced the1,4-cyclohexane methnol which has a special six-membered ring to modified PBS. A series of poly(butylene succinate-co-1,4-cyclohexane dimethanol succinate)(PBS-co-PCS)random copolyesters were synthesized by polycodensation reaction.The structure and physical properties of the aliphatic polyesters were characterized by hydrogen nuclear magnetic resonance spectrum(1H-NMR), Fourier transform infrared spectroscopic(FT-IR), differential scanning calorimetry(DSC), thermogravimetry analysis(TGA), X-ray diffraction(XRD) and lipase enzymatic degradation test. FT-IR and1H-NMR analysis showed that the synthetic copolymers were the expected products. XRD showed that the crystal structure of copolyesters changed with the increasing of CHDM component and the cocrystallization behavior had appeared. DSC test showed that the melting point(Tm) of the product decreased from113.7℃to64.6℃, and then increased to114.2℃,the glass transition temperature(Tg) decreased monotonously from the-33.8℃to the-58.7℃. TGA analysis indicated that copolymers had better thermal stability with the increasing content of1,4-cyclohexane dimethanol. The lipase enzymatic degradation test indicated that the copolyesters P51and P31had better degradability, when the content of PCS reached25mol%, the copolyester had the fastest degradative rate.From the chapter2, we can found that the eutectic behavior appeared, which influenced the degradation of polyesters. Therefore, in the chapter3we choosed1,3-butanediol to take the place of1,4-butanediol to improve the degradability by introducing methyl side group to reduce regularity. A series of biodegradable Poly(1,3-butylene succinate-co-1,4-cyclohexane dimethanol succinate) random copolyesters were synthesized by polycodensation reaction. FT-IR and1H-NMR analysis showed that the synthetic copolymers were the expected products. XRD showed that the crystal structure of copolyesters increased with the increasing of CHDM component, moreover the polyester tend to amorphous state when the molar mass of CHDM content reached fifty percent. DSC test showed that with the increasing of CHDM component, the melting point(Tm) and the glass transition temperature(Tg) gradually increased. TGA analysis indicated that the copolyester had higher themal stability with the increasing content of CHDM, which expand the application field of biodegradable polymer. The lipase enzymatic degradation test indicated that the copolyesters P11and P12had better degradability, which due to they all had lower crystallinity and their suitable degradation temperature were more closer to37℃.From the chapter1and chapter2, we all pound that the handling characteristics hadn’t greatly improved, which illustrated that pure six-membered ring couldn’t reach the purpose to increase the handling characteristics. So in the chapter4, we used H12MDI as chain extender to increase the handling characteristics. Biodegradable poly(ester urethane)s(PPBSCs) were obtained through chain-extension reaction of prepolymers, poly(butylene succinate)(PBS-OH) and poly(1,4-cyclohexane dimethanol succinate)(PCS-OH) using H12MDI as chain extender. PBS-OH and PCS-OH were all synthesized by melting polycondensation reaction. The structure and composition of PPBSCs was characterized by H-NMR and FT-IR, the molecular weight of prepolymers of PBS-OH and PCS-OH were17410and22886calculated by the results of1H-NMR. XRD showed that the crystal was caused by PBS chain segment when the molar ratio of PBS and PCS was higher than one to one, while the crystal caused by PCS chain segment when the molar ratio of PBS and PCS was less than or equal to one to one. DSC test showed that the melting point(Tm) of the product was among108.2℃and113.7℃, the glass transition temperature(Tg) increased monotonously from-18.2℃to5.6℃. The thermal stability of polymers were measured by TGA, it showed that PPBSCs had great thermal stability. The test of water absorption showed that the novel poly(ester urethane) PPCLBST had better hydrophilic ability than that of PBS. The result of hydrolytic degradation test indicated that the polyester polyurethane had good degradation property.