Measurement of Diffusion Coefficient of Monomers in Polymers

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08650894
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 化学工学一般
• Research Institution: HIROSHIMA UNIVERSITY
• Principal Investigator: TAKISHIMA Shigeki Faculty of Engineering, HIROSHIMA UNIVERSITY Associate Professor, 工学部, 助教授 (10188120)
• Co-Investigator(Kenkyū-buntansha): ZHONG Chongli Faculty of Engineering, HIROSHIMA UNIVERSITY Reseaarch Associate, 工学部, 助手 (50274113) ; SATO Yoshiyuki Faculty of Engineering, HIROSHIMA UNIVERSITY Research Associate, 工学部, 助手 (50243598) ; MASUOKA Hirokatsu Faculty of Engineering, HIROSHIMA UNIVERSITY Professor, 工学部, 教授 (50034385)
• Project Period (FY): 1996 – 1997
• Keywords: Diffusion Coefficient / Solubility / Polymer / Equation of State

Research Abstract

In this work, solubilities and diffusion coefficients were measured for nitrogen and ethylene in high-density polyethylene (HDPE) and two linear low-density polyethylenes (LLDPE) having different 1-hexene contents. The measurement was carried out using an apparatus based on the electricbalance method at temperatures of 333.2,353.2,403.2 and 433.2 K and at pressures up to 3.5 MPa. Moreover, measured solubilities and diffusion coefficients were correlated with Sanchez-Lacombe equation of state and Vrentas-Duda theory, respectively. From the investigations, the followings wree found :
1. For the nitrogen - polymer systems, solubilities increased with increasing temperature, showing so-called reverse solubility that is common for gases with low critical temperatures. Degree of crystaliinity, that was determined from temperature dependence of Henry's constants, decreased with increasing temperature. Diffusion coefficients represented little concentration dependence. Temperature dependence of the diffusion coefficients was also small in the temperature range examined, where the diffusion coefficients increased about one ordr of magnitude with an increase in temperature.
2. For the ethylene - polymer systems, solubilities decreased with increasing temperature, showing a usual temperature dependence. The solubilities of ethylene in amorphous regions of two LLDPE were almost the same despite different 1-hexene content. Ethylene showed about 7 times larger solubilities in the polymers thatn nitrogen. Diffusion coefficients of ethylene **vcaled remarkable temperature dependence. Concentration dependence of diffusion coefficients was also large at low temperatures.