Effect of soft/hard segments in poly (tetramethylene glycol)-Polyurethane for water barrier film

•Synthesis of thermoplastic polyurethanes with the similar molecular weight but different soft/hard segment ratios.•Different soft/hard segment ratio used as a key to control the phase separation and absorption blocks of thermoplastic polyurethanes.•Effects of soft/hard ratios on the water-vapor barrier property, which leads to the reinforcing encapsulation performance of thermoplastic polyurethane. A series of thermoplastic polyurethanes (TPUs) with the same molecular weight but different soft/hard ratios were synthesized by in-situ condensation polymerization using poly (tetramethylene glycol) (PTMG) as the polyol and methylene diphenyl diisocyanate (MDI) as the isocyanate. The weight fractions of the hard segments were varied from 0.0 to 0.4. The structures of the TPU series were analyzed by Fourier transform infrared spectroscopy and gel permeation chromatography. The changes in the thermal and optical properties due to the hard segment crystallinity were also measured by differential scanning calorimetry and UV–vis spectroscopy. Increasing the hard content promoted phase separation and served as absorption blocks in the TPU. The water vapor permeability of the TPU films with different soft/hard ratios ranged from 223.63 to 116.26 g/m2 day.