动态热机械分析技术在高分子形状记忆效应表征中的应用进展

Progress in Application of Dynamic Thermomechanical Analysis Technique in Characterization of Polymeric Shape Memory Effects

形状记忆高分子(SMP)是指能够感知外界环境变化的刺激并响应这种变化,对其自身状态参数进行调整,从而回复到预先设定状态的一类高分子材料。目前SMP除能够实现研究最为广泛的不可逆双重形状记忆效应外,也能够展现复杂的三重形状记忆效应、多重形状记忆效应、恒定外力下的可逆双向形状记忆效应、无外力的可逆双向形状记忆效应及其形状可重构效应。通常聚合物的形状记忆效应能够使用动态热机械分析技术进行表征,通过控制SMP的应力、应变和温度能够实现变形、暂时形状的固定和形状的回复,从而得到应力-应变-温度循环热机械曲线,实现定量形状记忆性能,包括形状固定率(R_(f))、形状回复率(R_(r))、形状回复速率(V_(r))和形状回复力等。本文综述了动态热机械分析仪(TA-Q800)的拉伸模式在各种形状记忆效应表征中的应用,包括测试程序的选择、程序设置及其相对应的热机械循环曲线、参数计算和测试条件对形状记忆效应的影响,最后分析了研究中存在的问题并展望了未来发展方向。

The shape memory polymers refer to a class of intelligent materials that sense changes in the external environment,respond to such changes,adjust to its own state parameters and return to a preset state.At present,SMP can not only realize the most widely studied irreversible double shape memory effect,but also exhibit complex triple shape memory effect,multiple shape memory effect,reversible two-way shape me-mory effect under constant external force,and reversible two-way shape memory effect without external force and shape reconfigurable effects.Generally,the shape memory effect of polymers can be characterized using dynamic thermomechanical analysis techniques.By controlling the stress,strain and temperature of the SMP,deformation,temporary shape fixation and shape recovery can be achieved,thereby obtaining a stress-strain-temperature cycle thermomechanical curves to achieve quantitative shape memory performance,including shape fixation ratio(R_(f)),shape recovery ratio(R_(r)),shape recovery speed and shape recovery force,etc.This paper reviews the application of the tensile mode of the dynamic thermomechanical analyzer(TA-Q800)in the characterization of various shape memory effects,including the selection of test programs,program settings and their corresponding thermomechanical cycle curves,parameter calculations,and influences of test conditions on shape memory effects.It ends with a critical and prospective discussion on problems existing in the current research and future development trends of this field.