Poly(1,5-pentylene-co-2,2,4,4-tetramethyl cyclobutylene terephthalate) copolyesters with high Tg and improved ductility and thermal stability

Poly(1,5-pentylene-co-2,2,4,4-tetramethyl cyclobutylene terephthalate) (PPecBT) random copolyesters glass transition temperature up to 136 °C were synthesized through two-step melting polycondensation of dimethyl terephthalate (DMT) or terephthalic acid (TPA), 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) and 1,5-pentanediol (PeDO). They were characterized and assessed with intrinsic viscosity , 1 H NMR, DSC , TGA , tensile and impact testing as well as melt foaming observation. Using PeDO as a diol comonomer was helpful to depress CBDO sublimation and pipeline blocking, and to reduce the composition and cis -trans ratio deviations between monomer and copolymer . The presence of PeT repeat unit in PPecBT was beneficial to improve the thermal stability of PPecBT and to reduce undesired melt foaming and volume expansion during melt processing. The T g of these amorphous copolymers is determined by intrinsic viscosity, copolymer composition and cis -cB unit fraction, and a quantitative relationship among them is established. Futhermore, these PPecBTs showed superior tensile ductility as well as strength and modulus.