超临界CO_2及共溶剂作用下聚碳酸酯的结晶和熔融行为

Effect of Supercritical CO_2 and Cosolvent on the Crystallization and Melting Behavior of Bisphenol-A Polycarbonate

采用差示扫描量热法 (DSC)研究了在超临界CO2 以及超临界CO2 +乙醇作用下温度和压力对聚碳酸酯的结晶和熔融行为的影响 .结果表明超临界CO2 能使聚碳酸酯 (PC)在其玻璃化转变温度下结晶 .CO2 是非极性流体 ,加入共溶剂能增加超临界流体的极性 ,提高流体的溶解能力 .与纯CO2 条件比较 ,少量共溶剂的加入使PC的结晶更加完善 。

The influences of temperature and pressure on the melting behavior of PC treated by supercritical CO2 and CO2 + C2H5OH have been studied by differential scanning calorimetry ( DSC). Supercritical CO2 depresses the crystallization temperature of PC and induces crystallization below the glass transition temperature. CO2 has no dipole moment and only a small quadrupole moment and, therefore, is essentially a nonpolar fluid. The addition of a small amount of a polar cosolvent is equivalent to giving the mixed fluid an overall small dipole moment. Similar annealing condition in the presence of supercritical CO2 + C2H5OH leads to more stable crystals. The addition of a small amount of C2H5OH as a cosolvent can induce crystallization at much lower temperature and pressure. In addition to its own plasticizing effect, supercritical CO2 acting as a carrier which delivers the polar component uniformly into the polymer matrix.