A Study of Glass Transition of Polymeric Materials by Specific Heat Spectroscopy

1.采用本实验室自行研制的交流量热实验系统。将系统中使用的锁定放大器替换为FFT分析器，缩短了测量时间。传统的交流量热系统采用带孔旋转平板作为光调制器对样品进行周期性加热。在该方案中，采用两片偏振片作为光调制器，其中一片是旋转的，另一片是固定的，以获得正弦光强。通过使用步进电机，加热频率变得更加精确。修改了PC机控制整个实验系统的程序，以适应FFT分析仪和步进式迫击炮控制器。利用新的程序，可以成功地改变加热频率进行测量。对分子量为2000的聚晶进行了初步测量。测量时间不到传统方法使用锁定放大器测量时间的十分之一。本课题的主要目标是缩短测量时间。这一新的实验系统将推动对聚合物材料性能至关重要的热历史的研究。目前加热频率限制在0.5-30赫兹范围内。扩大频率范围仍是一个未来的问题。

1. An experimental system of AC calorimetry constructed in our laboratory was used. The lock-in amplifier used in the system was replaced with FFT analizer to make measuring time shorter.2. Conventional AC calorimetry system uses a rotating plate with holes as the light modulator for periodic heating of the sample. In this project two polarizing plates, one of which is rotated and the other is fixed, were employed as the light modulator to obtain sinusoidal light intensity. The heating frequency became much more accurate by using a stepping motor.3. The program of the personal computer to control the whole experimental system was changed to fit the FFT analyzer and the stepping mortar controller. Using the new program we can make measurement changing the heating frequency successively.4. Preliminary measurement was made for Polystylen (MW=2000). The measuring time was less than one tenth of the measuring time of the conventional method using a lock-in amplifier. The main object of this project to make the measuring time shorter was carried out. Study of the thermal history which is important for the properties of polymeric materials will be progressed by this new experimental system.5. The heating frequency is limited in the range of 0.5Hz to 30Hz at present. To expand the frequency range is left as a future problem.