Abstract:

A novel apparatus for in situ optical measurement of glass transition temperature （T_g）was developed.The apparatus consisted of a high-pressure cell equipped with quartz windows, a data acquisition system, a heating and temperature-controlling system, a pressure-controlling system, and a CO₂ feeding system.The volume changes of poly-(ethylene-terephthalate) (PET) when it was swollen by CO₂ were measured in real-time by the apparatus, at the temperatures of 50, 60, 70, 80, 90, 100 and 120℃, and under the pressures of 0.1, 5, 10, 15, 20 MPa of CO₂.Consequently, the glass transition temperatures in SC-CO₂ were obtained under various conditions as indicated above.To examine the accuracy and reliability of this method, comparison of the results obtained by the apparatus under atmospheric pressure with those obtained by the standard differential scanning calorimetry (DSC) were made, and these two methods produced results within acceptable precision (1.6%).Thus the method developed in this work can be reliably used to measure the glass transition temperature of polymers in SC-CO₂.

Key words:

玻璃化转变温度, 超临界二氧化碳, 聚合物, 光学法

摘要：

研制了一套原位光学法测定超临界二氧化碳（SC-CO₂）介质中聚合物玻璃化转变温度（T_g）的仪器装置。该仪器装置由带石英视窗的高温高压平衡釜、数据采集系统、加热与温度控制系统、压力控制系统、CO₂输送系统5部分组成。采用该仪器装置，测定了温度为50、60、70、80、90、100、120℃，压力为0.1、5、10、15、20 MPa范围内，PET聚酯薄膜样品的体积溶胀率及相应的玻璃化转变温度。常压测量结果与DSC差示扫描量热仪的测量值吻合很好，在10 MPa下的实测结果与文献值亦具可比性，表明该实验装置的可靠性及研究方法的可行性。因此，本仪器装置及方法可用于测量SC-CO₂介质中聚合物的玻璃化转变温度。

关键词:

玻璃化转变温度, 超临界二氧化碳, 聚合物, 光学法