热致形状记忆聚合物的热力学性能

Thermomechanical Properties of Shape Memory Polymer

形状记忆聚合物作为一类新型功能材料,具有独特优点,近年来在机理研究和工程应用方面均受到高度重视。由于其功能实现主要是通过热激励实现的,建立其热力学本构方程是开展该类功能材料变形机理研究的基础。本文首先通过单拉伸实验研究了热致形状记忆聚氨酯在预应变分别为0%、5%、10%和20%下的形状冻结和恢复性能。考虑其冻结/恢复时间延迟效应、应力松弛效应以及热变形效应的影响,对其变形过程进行了理论分析。结果证实,理论预测值与实验测试结果较为吻合。

As a new class of functional materials,shape memory polymers（SMPs） attract scientific research and engineering applications attention due to their unique advantages.Thermomechanical constitution is critical for the understanding of their deformation mechanism since the function realization of SMPs is mainly realized by heat stimulus.Based on systematic thermomechanical experiments of shape memory polyurethane under different pre-strains,a constitutive model was proposed.Some affecting factors,e.g.time-retardment,stress-relaxation and thermal stress during frozen/recovery processes,were considered.The time-retardment coefficient and stress-relaxation function were introduced.The results exhibit that the frozen transition temperature is lower than the glassy transition temperature of the material while the recovery transition temperature is higher than that of the material.By introducing a temperature-dependant stress-relaxation factor,the viscoelastic effect can be effectively simulated.Theoretical results confirm to be much agreeable with the testing values.