关键词: 焓松弛, 位形熵, 玻璃化转变, 脆度, 山梨醇, 差示扫描量热法

Enthalpy relaxation dynamics of amorphous D-sorbitol has been studied by differential scanning calorimetry (DSC). A series of specific heat capacity curves (c_p(T)) were measured on heating (10 K•min^－1) after cooling the sample at different rates ranged between 0.5 and 20 K•min^－1. A phenomenological model of enthalpy relaxation based on the evolution of configurational entropy (GR model) was used to simulate the experimental data. All the experimental traces can be fairly well reproduced by this model, no matter whether a metastable limit state of relaxation process is assumed. The physically reasonable model parameters seemed to be independent of thermal history, except the nonexponential parameter, which increased slightly as the cooling rate increasing. The model parameter sets obtained under lower cooling rates show better predictive ability than those obtained under higher ones. Since the calculated relaxation time value is strongly dependent on the “fixed parameter” value, the predictive ability to the c_p(T) curves is not the only criterion for the determination of relaxation time. Take the limit fictive temperature as T_g in the fragility calculation leads to an significantly smaller value than the published data.

Key words: enthalpy relaxation, configurational entropy, glass transition, fragility, D-sorbitol, differential scanning calorimetry (DSC)