Modulated differential scanning calorimetry in the glass transition region
Modulated differential scanning calorimetry in the glass transition region
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DOI：
10.1007/bf01987421
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发表时间：
1997-07
期刊：
影响因子：
--
通讯作者：
Bernhard Wunderlich;I. Okazaki
中科院分区：
文献类型：
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作者：
Bernhard Wunderlich;I. Okazaki
温度调制量热法（TMC）允许从准等温实验中对玻璃化转变的动力学参数进行实验评估。本文基于实验数据，给出了调制差示扫描量热计（MDSC）通过玻璃过渡区加热和冷却时的总和反向表观热容量随加热速率和调制频率的函数模型计算。以非晶态聚对苯二甲酸乙二醇酯（PET）为例，拟合了简单的一级动力学模型。总热流携带迟滞信息（焓弛豫，热历史）和由于玻璃化转变引起的调制频率变化的指示。反向热流允许评估一次和更高次谐波的表观热容。计算是通过多达5000步的数值积分进行的。可以将计算结果与实验结果进行比较。当从平衡状态（即液态）进一步移动时，必须使用合作动力学来匹配模型和实验。
Temperature-modulated calorimetry (TMC) allows the experimental evaluation of the kinetic parameters of the glass transition from quasi-isothermal experiments. In this paper, model calculations based on experimental data are presented for the total and reversing apparent heat capacities on heating and cooling through the glass transition region as a function of heating rate and modulation frequency for the modulated differential scanning calorimeter (MDSC). Amorphous poly(ethylene terephthalate) (PET) is used as the example polymer and a simple first-order kinetics is fitted to the data. The total heat flow carries the hysteresis information (enthalpy relaxation, thermal history) and indications of changes in modulation frequency due to the glass transition. The reversing heat flow permits the assessment of the first and higher harmonics of the apparent heat capacities. The computations are carried out by numerical integrations with up to 5000 steps. Comparisons of the calculations with experiments are possible. As one moves further from equilibrium, i.e. the liquid state, cooperative kinetics must be used to match model and experiment.