Study on the Vacuum Drying Characteristics of Polyether Thermoplastic Polyurethane Film

The polyether thermoplastic polyurethane pellets were pressed into films by a compression molding process. The effect of temperature on the vacuum drying characteristics of TPU films was studied, and the effective diffusion coefficient and diffusion activation energy during the drying process were calculated. Five drying kinetic models were selected to fit and analyze the vacuum drying process of TPU films, and the mechanical properties of TPU films before and after drying at different temperatures were investigated. The results showed that in the vacuum drying process of TPU films, increasing the drying temperature would speed up the drying rate and shorten the drying time, and the drying process of the TPU films mainly occurred in the deceleration stage. The two-phase diffusion equation well reflected the change law of the moisture ratio in the vacuum drying process of the TPU films. The effective moisture diffusion coefficient was calculated to be 2.26×10⁻¹⁰−7.28×10⁻¹⁰ m²/s, and the diffusion activation energy was 37.49 kJ/mol. In addition, the elongation at break of the polyether TPU films hardly changed due to water absorption and drying process, and vacuum drying below 60℃ significantly recovered the tensile strength reduced by water absorption.