采用原位光学法研究聚酯(PET)/CO_2,系统的玻璃化转变温度(T_g)与压力间的关系.在温度为50℃～120℃,压力为0.1 MPa～20 MPa范围内,PET薄膜样品的玻璃化转变温度的降低(T_g)与气体的压力(p)成线性关系,其斜率dT_g/dp≈-1.35℃/MPa,上述条件下的最大降幅△T_(g,max)=-26.7℃.在30MPa的文献值明显偏离△T_g～p直线,意味着在高压阶段,静压起主导作用,使PET样品的玻璃化转变温度升高.
The change of the glass transition temperature T_g of poly-(ethylene-terephthalate) (PET), due to the dissolved CO_2 has been measured as a function of the gas pressure p, using a novel in situ optical measuring apparatus. The results indicate that at 20 MPa, the T_g is depressed by 26 ℃. The depression in T_g is found to be linear with pressure, with dT_g/dP of-1.3℃/MPa. To examine the accuracy and reliability of this method, the comparison of the result obtained by the apparatus at atmosphere pressure with that obtained by the standard differential scanning calorimetry (DSC) was made, and it showed that these two methods produced results within acceptable precision. Thus the method developed in this work is reliable to be used to measure T_g of polymers in CO_2. The T_g value at 30 MPa reported in the literature, however, departs markedly from the present investigation on PET/CO_2 system, which implies that at a higher gas pressure an effect opposite to the plasticization becomes dominant due to the hydrostatic pressure exerted by the gas.
参考文献
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| [2] | 叶树明,蒋凯,蒋春跃,潘勤敏.超临界二氧化碳介质中聚合物玻璃化转变温度[J].化工学报,2009(01):254-259. |
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