Synthesis and characterization of aliphatic poly(amide urethane)s having different nylon 6 segments through non-isocyanate route

Abstract

Two nylon-6 oligomers having polymerization degrees of 4.99 and 3.55 terminated with H₂N– and HO– groups (H₂N-PA-OHs) were prepared by the ring-opening polymerization of caprolactam with ethanolamine at different molar ratios. These oligomers were transformed into HO–terminated nylon-6 oligomers (HO-PA-OHs) through reaction with excessive caprolactone. The transurethane polycondensation of HO-PA-OHs with a diurethanediol, i.e., 1,6-bis(hydroxyethyloxy carbonyl amino)hexane (BHCH), was carried out at 170 °C under normal pressure for 4 h and at 180 °C under a reduced pressure of 3 mmHg for 6.5 h. A series of aliphatic thermoplastic poly(amide urethane)s having different short nylon-6 segments (s-PAUs) was prepared. The s-PAUs were characterized by viscometry, gel permeation chromatography, FT-IR, ¹H-NMR, solid ¹³C CP MAS NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X-ray scattering and tensile tests. Results showed Mn above 29,762, Mw above 36,725, Tm between 128.73 and 171.69 °C, and initial decomposition temperature over 266.25 °C. Tensile strength reached 31.50 MPa with strain at break up to 447.49 %. Some urea linkages were formed during transurethane polycondensation.