Study On Synthesis And Properties Of PBS-based Copolyesters

In order to extend the application of poly(butylene succinate)(abbreviated as PBS)and improve the shortcomings of PBS,such as high crystallinity,low degradation rate,and poor ductility,copolymerization modification methods can be adopted.The composition and properties of the materials are changed by incorporating comonomers,laying a theoretical foundation for the further development and utilization of PBS.In this paper,the method of melt polycondensation was used to copolymerize the three monomers of 1,4-cyclohexanedicarboxylic acid(CHDA),isosorbide(IS),and 2,5-furandicarb-oxylic acid(FDCA)with 1,4-succinic acid(SA)and 1,4-butanediol(BDO),respectively.Poly(butylene succinate-co-butylene 1,4-cyclohexanedicarboxylate)(PBCS),poly(butylene succinate-co-isosorbide succinate)(PBIS),poly(butylene succinate-co-butylene 2,5-furandicarboxylate)(PBFS)were prepared.The structure and properties of three series of copolyesters were systematically studied.The crystalline melting behavior and non-isothermal crystallization kinetics of PBCS,PBIS and PBFS copolyesters showed:due to the reduced regularity of the molecular chain structure,the crystallization properties of each copolyester changed significantly compared to PBS.With the increase of the amount of CHDA,IS,and FDCA monomers,the melting point and crystallization temperature of the three series of copolyesters decreased regularly,and the relative crystallinity gradually decreased;at the same time,with the increase of the three monomers of CHDA,IS and FDCA,the semi-crystallization time of the three series of copolyesters became longer and the crystallization rate became slower.The morphological structure and mechanical properties of PBCS,PBIS and PBFS copolyesters showed that the addition of CHDA,IS and FDCA monomers increased,the toughness of each series of copolyesters improved to varying degrees,but the tensile strength reduced to a certain extent;As the impact strength increased,the increase in elongation at break of the copolyesters was particularly prominent.The maximum elongation at break of the three series of PBCS,PBIS,and PBFS copolyesters reached 1155%,717%,and 1011%,respectively;The fracture mode of PBS was brittle fracture,but the fracture mode of the three series of copolyesters gradually changed to the ductile fracture mode with the increase of the corresponding monomer.The thermal performance of PBCS,PBIS,PBFS copolyesters showed:with the increase of the amount of CHDA,IS,FDCA monomers added,the three series of copolyesters had higher thermal stability;In the nitrogen atmosphere,the thermal decomposition reaction of the copolyester was a first-order reaction,and the addition of the three monomers correspondingly increased the thermal decomposition activation energy of the copolyesters.The research results of dynamic mechanical properties and rotational rheological properties of three series of PBCS,PBIS,and PBFS copolyesters showed that when the glass state transitions to a high elastic state,with the increase in the amount of CHDA,IS,and FDCA monomers,the storage modulus of the copolyesters decreased,and the loss modulus increased first and then decreased.At the same time,the glass transition temperature gradually increased;In the viscous flow state,with the increase of the amount of CHDA,IS,and FDCA monomers,the viscosity of the corresponding series of copolyesters gradually decreased.The soil aging results of PBCS series copolyesters showed that the copolyesters were degraded to a certain extent with the increase of soil burial time,and the corresponding copolyesters showed better degradation performance with the increase of the amount of CHDA monomer.In the case of the same feed ratio,comparison with the three series of PBCS,PBIS,and PBFS copolyesters found that:(1)In terms of molecular weight,the molecular weight of PBIS series copolyester was the smallest;(2)In terms of mechanical properties,PBIS series copolyesters had the lowest impact strength and lowest tensile strength,PBFS series copolyesters were the second,and PBCS series copolyesters were the strongest;(3)In terms of thermal stability,all three series of copolyesters had higher thermal stability;(4)In terms of thermodynamic properties,IS and FDCA monomers had a greater effect on the molecular chain regularity of PBS-based copolyesters.Compared to pure PBS,as the amount of the two monomers increased,the melting point,crystallization temperature and glass transition temperature(T_g)of the corresponding copolyesters changed greatly.Among them,when the amount of IS material was 16.5%,the T_g of the copolyester was 0.2°C(the PBS was-22.1°C),and when the FDCA ratio was 13.5%,the T_g of the copolyester was-3.5?(the PBS was-23.7?).At the same time,the two copolyesters still had good mechanical properties.