抄録
The effects of annealing temperature on the micro-aggregation structure, the mechanical and melting properties of thermoplastic polyurethane elastomer (TPU) were investigated. TPU was composed of poly{(tetramethylene adipate)-co-(hexamethylene adipate)} glycol, 4, 4′-diphenylmethane diisocyanate and 1, 4-butanediol units. The TPU sheets prepared by injection molding were annealed at various temperatures from 23 to 120°C for 4h. Differential scanning calorimetry, pulsed nuclear magnetic resonance and dynamic viscoelastic measurements revealed that the degree of micro-phase separation of the TPUs became stronger with increasing annealing temperature owing to the progress of the formation of well-organized hard segment domains. Dynamic storage modulus of the rubbery plateau region around room temperature and the termination temperature of the rubbery plateau region decreased and increased with increasing annealing temperature, respectively. The temperature sweep experiments for molten TPUs indicated that the critical gel temperature at intersection between G′ and G″, increased with increasing annealing temperature. In addition, the TPUs showed the strain hardening of uniaxial elongation viscosity with increasing annealing temperature owing to residual hard segment domains at the operating temperature. It was revealed that the formation of well-organized hard segment domains by annealing strongly influences on not only mechanical properties but also melting ones of the TPUs.
