Crystallization of Polymers Induced by Supercritical Fluids

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 12450312
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 化学工学一般
• Research Institution: Hiroshima University
• Principal Investigator: MASUOKA Hirokatsu Hiroshima University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (50034385)
• Co-Investigator(Kenkyū-buntansha): SATO Yoshiyuki Hiroshima University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (50243598) ; TAKISHIMA Shigeki Hiroshima University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (10188120)
• Project Period (FY): 2000 – 2001
• Keywords: Supercritical carbon dioxide / Polylactide / Crystallization Rate

Research Abstract

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.