Crystallization kinetics of poly(L-lactide) in contact with pressurized CO2
Crystallization kinetics of poly(L-lactide) in contact with pressurized CO2
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DOI：
10.1002/pen.20017
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发表时间：
2004-01-01
影响因子：
3.2
通讯作者：
Ohshima, M
中科院分区：
文献类型：
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作者：
Takada, M;Hasegawa, S;Ohshima, M
采用高压差示扫描量热仪（DSC）研究了CO2对聚L-丙交酯（PLLA）等温结晶动力学的影响。结果表明，结晶速率符合Avrami方程。然而，结晶动力学常数根据结晶温度和溶解在PLLA中的CO2浓度而改变。在晶体生长速率控制区（自扩散控制区）的温度下，CO2加速了结晶速率，而在成核控制区则抑制了结晶速率。CO2还降低了玻璃化转变温度T-g和熔融温度T-m。因此，CO2诱导的结晶速率的变化可以从T-g和平衡熔融温度的降低幅度来预测。使用广角X射线衍射仪（WAXD）的结晶结构和结晶度的聚合物在接触加压CO2进行了研究。所得样品的结晶度随CO2的压力水平而增加，尽管CO2的存在并没有改变晶体结构。
The effect of CO2 on the isothermal crystallization kinetics of poly(L-lactide), PLLA, was investigated using a high-pressure differential scanning calorimeter (DSC), which can perform calorimetric measurements while keeping the sample polymer in contact with pressurized CO2. It was found that the crystallization rate followed the Avrami equation. However, the crystallization kinetic constant was changed depending upon the crystallization temperature and concentration of CO2 dissolved in the PLLA. The crystallization rate was accelerated by CO2 at the temperature in the crystal-growth rate controlled region (self-diffusion controlled region), and depressed in the nucleation-controlled region. CO2 has also decreased the glass transition temperature, T-g, and the melting, temperature, T-m. As a result, the CO2-induced change in the crystallization rate can be predicted from the magnitudes of depression of both T-g and the equilibrium melting temperature. The crystalline structure and crystallinity of polymers crystallized in contact with pressurized CO2 were also investigated using a wide angle X-ray diffractometer (WAXD). The resulting crystallinity of the sample was increased with the pressure level of CO2, although the presence of CO2 did not change the crystalline structure.