Synthesis and properties of non-isocyanate thermoplastic polyurethanes containing dibutylene terephthalate units

Abstract

Bis (4-hydroxybutyl) terephthalate (BHBT) was synthesized from the condensation of dimethyl terephthalate with excessive 1,4-butanediol. Transurethane polycondensation of 1,6-bis (hydroxyethyloxy carbonyl amino) hexane (BHCH) with BHBT at different BHCH/BHBT molar ratios was carried out at 170 °C under a reduced pressure of 3 mmHg for different time. A series of non-isocyanate thermoplastic polyurethanes (NI-TPUs) containing dibutylene terephthalate units were prepared. The NI-TPUs were characterized by gel permeation chromatography, FT-IR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X-ray scattering, and tensile test. The NI-TPUs exhibited M n above 14200, M w above 19700, T g between 25.1 and 35.1 °C, T m from 123.8 °C to 141.1 °C, initial decomposition temperature over 251.7 °C, and tensile strength up to 37.89 MPa with a strain at break of 475.28 %. NI-TPUs with high T m, good tensile strength and good toughness were prepared. Introduction of dibutylene terephthalate units improved the mechanical properties obviously. Some urea linkages were formed during transurethane polycondensation because of the back-biting side reaction the -HNCOOCH2CH2OH terminal groups.