At present, more and more attention has been paid to biodegradable and economical polymer materials in the world. Because of its biodegradability and economy, synthetic aliphatic polyesters have become one of the research hotspots at home and abroad. Methods are biological fermentation and chemical synthesis. The former is mainly used for the synthesis of hydroxy fatty acid esters (PHA), and the cost of the synthesized polymers is higher. The latter mainly synthesizes linear polyesters, adopts open loop and condensation, and can be used for molecular design of products with low cost.
Aliphatic polyesters have low melting points and cannot be used alone as plastics, with polyoxalates and polybutylene succinate being the exceptions. Polyoxalate is difficult to achieve because of its difficulty in achieving higher molecular weight and stability, and polybutylene succinate is favored for products that have good thermal stability and high molecular weight. Polybutylene succinate was only studied since the 1990s. At present, only Japan has small-volume commercial products.
The research goal of the Polymer Research Institute of the Department of Chemical Engineering of Tsinghua University is to prepare a biodegradable and economically sound polymeric material that can be directly applied to the packaging industry and agricultural plastic films, and at the same time reveal the mechanism of chain extension reaction and biological Degradation mechanism. They used chemical synthesis to synthesize linear polyester-polybutylene succinate. Synthesis is divided into esterification, post polycondensation reaction. Post-polycondensation can be carried out using a screw extruder in the presence of a vacuum chain extender; it can also be carried out under high vacuum at high temperatures. The products synthesized by this method are directly extruded and molded so that the production efficiency is improved. The chain extension reaction in this system has no precedent in the world at present.
The Institute has now completed the following work: by controlling appropriate reaction conditions and synthesizing or searching for novel catalysts, the product has a higher molecular weight; studied the catalytic polymerization reaction and its biodegradation mechanism; synthesized a variety of chain extenders, Prepolymerized polyester chain-extended chain extender allows the reaction to be completed in a screw extruder; different comonomers are used to copolymerize succinic acid and butanediol for linear polyesters Molecular design, adjusting its mechanical properties and biodegradability to meet application requirements in different fields; researching the relationship between the structure and properties of linear polyesters and the degradability of microorganisms under different conditions.
The molecular weight of the currently synthesized aliphatic polyester can be compared with Japanese products, and pilot production and expansion can be conducted, and the biodegradation mechanism and application of biomaterials can be further studied.