Separation of cis–trans CBDO and the effect of its cis–trans isomers on the properties of modified PET co-polyesters

2,2,4,4-Tetramethyl-1,3-cyclobutanediol (CBDO) modified co-polyesters are expected to replace bisphenol A polycarbonate applications in many fields, and the cis – trans isomerisation of CBDO directly affects the co-polyester properties. However, the separation of cis – trans CBDO isomers and the influence of cis–trans isomer ratio on the performance of co-polyester are poorly investigated at present. In this paper, an efficient method of separating cis – trans CBDO isomers was proposed, and CBDO modified PET co-polyesters (PEBT) with a total CBDO content of about 40 % and a cis -CBDO content of 20–100 % were synthesized by modulating the cis - content. The glass transition temperature (T g ) of the co-polyester with 100 % cis -CBDO was as high as 117.8 °C, and the increment in T g of the co-polyester with per mol of cis -CBDO introduced was calculated to be 0.92 °C, which was 2.7 times of the increment of trans -CBDO (0.34 °C). With the increase of cis -CBDO content from 20 % to 100 %, the tensile strength was correspondingly increased from 35.4 MPa to 40.2 MPa, and the elongation at break decreased from 74 % to 18 %, respectively. This paper provides a theoretical basis for the preparation of high-performance CBDO-modified co-polyesters.