采用模压成型工艺将聚醚型热塑性聚氨酯(TPU)粒料压制成膜,考察了TPU薄膜在不同温、湿度下的含水率变化规律,利用数学模型拟合TPU薄膜的含水率变化过程,并计算TPU薄膜的有效水分扩散系数和扩散活化能,最后对不同温、湿度下吸水平衡的TPU薄膜进行结构和力学性能测试分析。含水率测试表明,TPU薄膜的平衡含水率主要由湿度决定,而升高温度会缩短其吸水至平衡状态所需的时间。数学模型拟合表明,TPU薄膜的吸水过程符合一维Fick定律,其有效水分扩散系数在(1.60~5.92)×10-11m2/s之间,且随温度的升高而增大;水分扩散活化能约为30~40kJ/mol。结构分析表明,水分子会破坏TPU中原有的羰基氢键,并与游离羰基形成新的氢键。力学性能测试表明,TPU薄膜的拉伸强度随着温度和湿度的升高而下降,但断裂伸长率变化不大。
The polyether-type thermoplastic polyurethane (TPU) pellets were pressed into films by a molding process.The change law of water content of TPU film under different temperature and humidity was investigated,and the change process of water content of TPU film was fitted by a mathematical model.The effective water diffusion coefficient and diffusion activation energy of TPU film were calculated.Finally,the structure and mechanical properties of TPU film with water absorption balance under different temperature and humidity were tested and analyzed.The moisture content test showed that the equilibrium moisture content of the TPU film was mainly determined by humidity,and increasing the temperature shortened the time required for water absorption to equilibrium state.The mathematical model fitting indicated that the water absorption process of the TPU film conformed to one-dimensional Fick's law,and its effective water diffusion coefficient was between 1.60×10-11~5.92×10-11m2/s,which increased with the increase of temperature,and the activation energy of water diffusion was about 30~40kJ/mol.Structural analysis suggested that water molecules would break the original carbonyl hydrogen bonds in TPU and form new hydrogen bonds with free carbonyl groups.The mechanical properties test revealed that the tensile strength of TPU film decreased with the increase of temperature and humidity,but the elongation at break did not change much.
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