The Study Of Property Of Bacterial P[3HB-co-4HB] And Its Modified Production

Poly(3-hydroxylbutyrate-co-4-hydroxylbutyrate)[P(3HB-co-4HB)] is a kind of thermoplastic copolymer, possessing the biodegradability and biocompatibility ,which can be used in a lots fields such as implant applications, controlled drug release, food package, agriculture films and so on. However, its application is limited to a certain extent for brittleness, thermal stability and slow crystalline rate. In this paper, the effect of 4HB content on the properties of P(3HB-co-4HB) is discussed for the first time in detail, and some plasticizer, nucleation agent and PLA 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 time-dependent changes in molecular weights of melt samples are monitored and the effect of molecular weight on the properties of copolyester is first discussed. The results show as follow.With the increase of 4HB unit content, the melting temperature, glass transit temperature, storage mould, yield strength and strength at break decrease. At the same time, elongation at yield and break increase. The thermal stability and liquidity can be improved with the increase of 4HB content.The incorporation of plasticizer can reduce melting temperature, crystalline temperature and crystalline enthalpy of blends. At the same time, the effect of 20wt% TEC on crystalline property of copolymer with low 4HB content is bigger than that with high 4HB content.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 AOPS can make the crystalline peak sharper, and increase the number of spherulite. ft can promote the mechanical property and thermal stability of blends. The effect of OAPS is better than that of OIBS.It is revealed that the compatibility of P(3HB-co-4HB) with poly(lactic acid) (PLA) is poor. There are seriously phases separate on cross-section. And, incorporation of PLA can decrease the mechanical property and increase the thermal stability and.crystallinity of blends.And the time-dependent changes in molecular weights during the thermal degradation followed the kinetic model of random chain scission at ester groups. According to the decrease of molecular weight, the melting temperature increase, and glass transit temperature decrease. At the same time, both tensile strength and elongation at break decrease together. The melting index of copolymer increase and extruded product become smooth, so the processing property is improved with the decrease of molecular weight.