The synthesis and characterization of PTT-PBT copolymers

The PTT-PBT copolymers used in this work were prepared from PTA, BG, 1,3-PDO by the direct esterification at 20-liter reactor. Both C-13-NMR and H-1-NMR spectra of all copolymers show that PTT-PBT copolymers are block copolymers and the content of PBT unit incorporated into the copolymers is always less than that fed in the polymerization, i.e., the content of PTT unit is more than that fed in the polymerization. The intensity of the 1042cm(-1), 1469cm(-1), 2901cm(-1), 2967cm(-1) bands are decreased and the 775cm(-1) band shifts to the lower wavenumbers with increasing PBT content in the IR spectrum. The glass transition temperatures, melting temperatures and crystallization temperatures of PTT-PBT copolymers reduce when the PBT content increases. To the copolymer with rich PBT content, the crystallization and melting behaviors is similar to the PBT homopolymer. The thermal stability of the copolymers are slightly influenced by the composition, being better in nitrogen than in air. In the presence of oxygen, the thermal stability of all the samples is lower with increasing PBT content.