Sakatsuji Waki, Konishi Takashi, Miyamoto Yoshihisa
Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 Jul;88(1):012605. doi: 10.1103/PhysRevE.88.012605. Epub 2013 Jul 23.
The effects of thermal history on the enthalpy relaxation in polystyrene are studied by differential scanning calorimetry. The temperature dependence of the specific heat in the liquid and the glassy states, that of relaxation time, and the exponent of the Kohlrausch-Williams-Watts function are determined by measurements of the thermal response against sinusoidal temperature variation. A phenomenological model equation previously proposed to interpret the memory effect in the frozen state is applied to the enthalpy relaxation and the evolution of entropy under a given thermal history is calculated. The annealing below the glass transition temperature produces two effects on enthalpy relaxation: the decay of excess entropy with annealing time in the early stage of annealing and the increase in relaxation time due to physical aging in the later stage. The crossover of these effects is reflected in the variation of temperature of the maximum specific heat observed in the heating process after annealing and cooling.
通过差示扫描量热法研究了热历史对聚苯乙烯中焓松弛的影响。通过测量对正弦温度变化的热响应，确定了液态和玻璃态下比热的温度依赖性、弛豫时间的温度依赖性以及科尔劳施-威廉姆斯-瓦特函数的指数。将先前提出的用于解释冻结状态下记忆效应的唯象模型方程应用于焓松弛，并计算了给定热历史下熵的演化。低于玻璃化转变温度的退火对焓松弛产生两种影响：退火早期过量熵随退火时间的衰减以及后期由于物理老化导致的弛豫时间增加。这些影响的交叉反映在退火和冷却后加热过程中观察到的最大比热温度的变化上。
