Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (05): 1031-1038.doi: 10.3866/PKU.WHXB20110419

• THERMODYNAMICS, KINETICS, AND STRUCTURAL CHEMISTRY • Previous Articles     Next Articles

Effect of Annealing Conditions on Enthalpy Relaxation Parameters of D-Sorbitol Glass

YE Bin, GAO Cai, LIU Xiang-Nong, YANG Suo, JIANG Bin   

  1. School of Mechanical and Automotive Engineering, Hefei University of Technology, Hefei 230009, P. R. China
  • Received:2010-11-08 Revised:2010-12-29 Published:2011-04-28
  • Contact: GAO Cai E-mail:gao_cai@hotmail.com
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20803016) and Natural Science Foundation of Anhui Province, China (070414163).

Abstract:

We studied the enthalpy relaxation dynamics of amorphous D-sorbitol by differential scanning calorimetry (DSC). A series of specific heat capacities (Cp(T)) for D-sorbitol were measured upon heating of 10 K·min-1. The samples were subjected to thermal treatment involving isothermal annealing with different annealing time (ta). A new phenomenological model by Gómez Ribelles (the GR model) of enthalpy relaxation based on the evolution of configurational entropy was used to simulate the experimental data to verify the applicability of the GR model to small molecular glass. The results indicated that a single set of GR model parameters only reproduced the corresponding experimental Cp(T) curve of D-sorbitol fairly well. It failed to find a set of GR model parameters as the material constant independent of the thermal history. In contrast with other phenomenological models, some parameters of the GR model remained unchanged. The model parameter sets obtained under longer annealing time show better predictive ability. In contrast to the continuous cooling process for D-sorbitol, the ratio between the mean value of the limit state parameter (δ) and the increment of specific heat capacity at TgCp(Tg)) apparently increases, but the increase is less than that of polymers. The results brought into question if the metastable limit state introduced by the GR model applied to small molecular glass systems.

Key words: Enthalpy relaxation, Differential scanning calorimetry, Configurational entropy, D-sorbitol, Glass transition, Isothermal annealing, Fragility

MSC2000: 

  • O642