Effects of Poly(cyclohexanedimethylene terephthalate) on Microstructures, Crystallization Behavior and Properties of the Poly(ester ether) Elastomers

To understand the role of molecular structure on the crystallization behavior of copolyester in thermoplastic poly(ether ester) elastomers (TPEEs), series of poly(butylene-co-1,4-cyclohexanedimethylene terephthalate) (P(BT-co-CT))-b-poly(tetramethylene glycol) (PTMG) are synthesized through molten polycondensation process. The effects of poly(cyclohexanedimethylene terephthalate) (PCT) content on the copolymer are investigated by Fourier transform infrared spectroscopy (FT-IR), ¹H and 13C nuclear magnetic resonance (NMR), gel permeation chromatographs (GPC), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical, and visible light transmittance tests. FT-IR and NMR results confirm the incorporation of PCT onto the copolymer. WAXD and DSC indicate that the crystalline structure of the copolymers changed from α-PBT lattice to trans-PCT lattice when the molar fraction of PCT (MPCT) is above 30%, while both crystallization and melting temperatures reach the minima. An increase in MPCT led to an increase in the number sequence length of PCT, the thermal stability and the visible light transmittance of the copolymer, but to a slight decrease in tensile strength and elastic modulus.