Crystallization of Polymers Induced by Supercritical Fluids

超临界流体诱导聚合物结晶

• 批准号: 12450312
• 负责人: MASUOKA Hirokatsu
• 金额: $ 9.66万
• 依托单位: Hiroshima University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12450312/
• 关键词: Supercritical carbon dioxide; Polylactide; Crystallization Rate; 結晶化; 溶解度; 二酸化炭素

Crystallization rate of polylactide induced by supercritical carbon dioxide was measured with a FT/IR spectrometer equipped with a high-pressure diamond ATR cell. Absorbance change at 1266 cm^<-1> was related with crystallinity obtained from X-ray diffraction (XRD). It is hard to extract the crystallization rate from experimental observation, because solute diffusion rate in polymer is usually small and the crystallization follows sorption of the solute. The ATR method used in this work, however, will measure only the crystallization rate, because polymer sample can be thinner (about 10 μm) in this method and sorption equilibrium accomplished less than 9 s. The crystallization rate of four kinds of sample thickness (10, 50, 100, and 250 μm) was measured to make sure this. While the rate of the absorbance change decreased with increasing the thickness of the 100 and 250 μm sample, sample thickness dependence on the rate did not be observed in the sample thickness of 10 and 50 μm. Therefore, we used the samples of thickness from 10 to 20 μm. The crystallization did not be observed with XRD at CO_2 treatment pressure of 1 and 2 MPa, whereas the crystallization was observed with FT/IR. This observation means possibility of small crystallite existence, which can not be detected with XRD. DSC measurement of CO_2 treated sample was carried out to make sure the existence. The crystallization temperature decreased with increasing the increasing the treatment pressure. This result means the existence of small crystallite. The crystallization mechanism was made clear through the absorbance change measurements. The mechanism consists of two steps, at first small crystallite rapidly forms and then growth of the crystallite begins.

用FT/IR光谱仪和高压金刚石ATR池测定了聚乳酸在超临界CO2诱导下的结晶速率。在1266 cm-1处的吸光度变化<-1>与从X射线衍射（XRD）获得的结晶度相关。由于溶质在聚合物中的扩散速率通常很小，而且结晶是在溶质吸附之后进行的，因此很难从实验观测中提取结晶速率。然而，本工作中使用的ATR方法将仅测量结晶速率，因为在该方法中聚合物样品可以更薄（约10 μm），并且吸附平衡在9 s内完成。测量了四种样品厚度（10、50、100和250 μm）的结晶速率以确保这一点。100 μ m和250 μm样品的吸光度变化率随厚度的增加而降低，而10 μ m和50 μm样品的吸光度变化率与样品厚度无关。因此，我们使用厚度为10 - 20 μm的样品。在1 MPa和2 MPa的CO_2处理压力下，XRD没有观察到晶化现象，而FT/IR却观察到了晶化现象，这意味着可能存在XRD无法检测到的小晶粒。对CO_2处理后的样品进行了DSC测试，以确定其存在。晶化温度随处理压力的增加而降低。这一结果意味着小晶粒的存在。通过吸光度变化的测量，明确了结晶机理。该机制由两个步骤组成，首先快速形成小晶粒，然后开始晶粒的生长。