物理化学学报 >> 2011, Vol. 27 >> Issue (05): 1031-1038.doi: 10.3866/PKU.WHXB20110419

热力学,动力学和结构化学 上一篇    下一篇

退火条件对山梨醇玻璃焓松弛参数的影响

叶斌, 高才, 刘向农, 杨锁, 江斌   

  1. 合肥工业大学机械与汽车工程学院, 合肥 230009
  • 收稿日期:2010-11-08 修回日期:2010-12-29 发布日期:2011-04-28
  • 通讯作者: 高才 E-mail:gao_cai@hotmail.com
  • 基金资助:

    国家自然科学基金(20803016)和安徽省自然科学基金(070414163)资助项目

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).

摘要:

采用差示扫描量热法(DSC)测定山梨醇样品经历不同时间(ta)等温退火后, 以10 K·min-1速率进行升温时玻璃化转变温度(Tg)前后的比热容(Cp(T)). 将Gómez Ribelles (GR)提出的一种基于构型熵的现象学模型用于描述山梨醇玻璃的焓松弛行为, 考察GR模型能否适用于小分子玻璃体系. 结果表明, 单组GR模型参数拟合的曲线均能较好重现对应热历史条件下的山梨醇体系的实验所得Cp(T)曲线, 尽管并未找到不随热历史而变的一组参数作为材料常数, 但与其它现象学模型应用于小分子玻璃时, 其模型参数都随热历史变化而变化的特点相比, GR模型的某些参数基本保持不变. 且在较长退火时间下拟合得到的模型参数普适性较好. 同经历连续降温的山梨醇相比, 等温退火过程得到的松弛极限态参数(δ)的平均值与Tg处比热容增量(ΔCp(Tg))的比值明显增大, 但仍小于聚合物的值, 表明GR模型提出的亚稳极限态对小分子玻璃的影响值得商榷.

关键词: 焓松弛, 差示扫描量热法, 构型熵, 山梨醇, 玻璃化转变, 等温退火, 脆度

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