高聚物自由体积与温度和应力水平的相关性

EFFECTS OF TEMPERATURE AND STRESS LEVEL ON THE FREE VOLUME IN HIGH POLYMERS

高聚物等粘弹性材料力学行为的时间相关性,可采用材料内部时钟或特征时间表征。这个特征时间受多种因素的影响,如温度、物理老化、压力和溶剂浓度、损伤、应力水平或应变水平等。文中考察温度和应力水平对材料特征时间的影响,得到了材料粘度与温度和应力水平的相互关系,进而推导出材料中自由体积分数与温度及应力水平的相互关系式,为拓展时间-温度等效原理和建立时间-温度-应力等效原理提供了理论基础。

Time dependence of mechanical behavior of viscoelastic materials, such as high polymers, reveals the assumption of an intrinsic time o′clock, which can be influenced by many factors such as temperature, physical aging, pressure, solvent concentration, damage, strain and stress levels, etc. The changes in intrinsic time of viscoelastic materials are usually studied in the framework of the free volume theory. In this paper, the dependence of intrinsic time of viscoelastic materials on the combination of applied stress level and temperature was investigated. The correlation between material viscosity or free volume and its two influencing factors (i.e. temperature and stress level) was derived. Based on the free volume theory and the obtained formulae, the time-temperature-stress equivalence principle was preliminarily proposed.