Exclusion effect of carbon dioxide on the crystallization of polypropylene
Exclusion effect of carbon dioxide on the crystallization of polypropylene
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DOI：
10.1002/polb.20076
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发表时间：
2004-05
期刊：
影响因子：
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通讯作者：
Takafumi Oda;H. Saito
中科院分区：
文献类型：
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作者：
Takafumi Oda;H. Saito
利用数字化高保真显微镜和高压可视化装置，对等规聚丙烯在不同CO2压力和温度下的结晶生长过程进行了原位观察。在高于2 MPa的压力下，在CO2下结晶，球晶内的原纤被扭曲和分支，这表明从原纤的生长前沿排除CO2。在140 °C时，球晶生长速率（G）随CO2压力的增加而增加，在0.3MPa附近达到最大值，然后下降。当压力大于6 MPa时，反应速率比常压下的空气慢。用Hoffman-Lauritzen理论分析了结晶动力学，发现G的压力依赖性是由于可结晶分子的输运速率（βg）随压力的变化而变化，即βg随压力先增大后减小。在低压下βg的增加是由于CO2的增塑作用，而在高压下βg的降低是由于CO2被排除在晶体生长前沿之外。© 2004 Wiley Periodicals，Inc.聚合物科学杂志B部分：聚合物物理42：1565-1572，2004
We investigated the crystallization growth of isotactic polypropylene under carbon dioxide (CO2) at various CO2 pressures and temperatures by in situ observation with a digital high-fidelity microscope and a specially designed high-pressure visualized cell. The fibrils within the spherulite were distorted and branched by crystallization under CO2 at pressures higher than 2 MPa, and this suggested the exclusion of CO2 from the growth front of the fibrils. The spherulite growth rate (G) at 140 °C increased with the CO2 pressure, attained a maximum value around 0.3 MPa, and then decreased. Above 6 MPa, it became slower than that under air at the ambient pressure. An analysis of the crystallization kinetics by the Hoffman–Lauritzen theory revealed that the pressure dependence of G could be ascribed to the change in the transportation rate of crystallizable molecules (βg) with pressure; that is, βg increased and then decreased with pressure. The increase in βg at a low pressure was caused by the plasticizing effect of CO2, whereas the decrease in βg at a high pressure was due to the exclusion of CO2 from the crystal growth front. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1565–1572, 2004