Investigation of soft segments of thermoplastic polyurethane by NMR, differential scanning calorimetry and rebound resilience

Abstract

The microscopic and macroscopic properties of a series of thermoplastic polyurethane (TPU) samples with different content in the hard segments and different molecular weight of the soft segments were investigated. Proton NMR transverse magnetization relaxation, DSC and rebound resilience techniques were used to characterize their molecular chain mobility, phase composition, glass transition temperature and angle of rebound. The increase of the hard segments content at the same molecular weight soft segments leads to an increase of the glass transition temperature as determined by DSC and to a decrease of the angle of rebound as determined by rebound resilience. These quantities can be correlated to the decrease in the effective transverse relaxation rates of the soft segments and to the increase of the relative fraction of the hard segments as determined by NMR. By increasing the molecular weight of the soft segments at the same content of the hard segments, the glass transition temperature and the angle of rebound decrease and the effective transverse relaxation time of the soft phase increases.