The Degradation Properties And Modification Poly(3-hydroxylbutyrate-co-4-hydroxylbutyrate)

Poly(3-hydroxylbutyrate-co-4-hydroxylbutyrate)[P(3HB-co-4HB)] is a kind of thermoplastic copolymer, which is synthesized and stored in the cell cytoplasm by various microorganisms. This biological polyester has greatly attracted the attention of people due to their biodegradability and biocompatibility. Compared to polyester Poly(3-hydroxybutyrate)(PHB), P(3HB-co-4HB) varys from hard crystalline plastics to elastic rubbers depending on its composition. Moreover, the rate of degradation of P(3HB-co-4HB) in various environments can be controlled by judiciously altering its monomer compositions. However, its application is limited to a certain extent for brittleness, thermal stability and slow crystalline rate. In this paper, nucleation agent such as BN,3988, BA1, N11, N21, OPS, OIBS and PLLA are added or blended in order to improve the property of P(3HB-co-4HB). At the same time, the thermal, crystalline and mechanical properties of the modified production are investigated. At last, the effect of4HB fraction on the degradation properties of P(3HB-co-4HB) is discussed. The nucleation modification is an important method. The additive of nucleating agent can increase nucleation density, improve crystallization rate. Blending materials of P(3HB-co-4HB)/nucleation agents are prepared by solution casting method and melting molding method. The results showed that POSS can improve the crystalline property of P(3HB-co-4HB) as a nucleation agent. Moreover, OAPS and OIBS were further investigated. The addition of OAPS can make the crystalline peak sharper, and increase the number of spherulite. It can promote the mechanical property and thermal stability of blends. The effect of OAPS is better than that of OIBS.Second, blending materials of P(3HB-co-4HB)/PLLA were prepared by solution casting method. Two kinds of P(3HB-co-4HB) with different monomer composition were choosed. One is thermoplastics: P(3HB-co-10%4HB) with high tensile strength and small breaking elongation, the other is rubber-like materials:P(3HB-co-21%4HB) with high breaking elongation and small tensile strength. The results showed that the compatibility of P(3HB-co-4HB) with PLLA is poor. And, the incorporation of PLLA increased the thermal stability, and incorporation of P(3HB-co-4HB) extended breaking elongation and increased the degradation rate. The effect of P(3HB-co-21%4HB) is better than that of P(3HB-co-10%4HB). Finally, the effect of4HB fraction on the degradation in soil and by lipase was investigated. It was found that degradation rate of P(3HB-co-4HB) films both in soil and by lipase increased as the4HB fraction increased; the effect of4HB fraction on the degradation by lipase is less than degradation in soil; the4HB fraction has a great influence on the corrosion morphology.