Measurement of solubilities and diffusion coefficients of carbon dioxide in polymers at high temperatures and high pressures

摘要

Gas solubility and diffusion coefficient are important properties in polymer processing, polymerization, and devolatilization. A new system was developed based on a gravimetric method using a magnetic suspension balance that is applicable up to 350°C and 20 MPa. Fluctuation of temperature, pressure, weight at 305°C and 20 MPa, were less than ±0.03 K, ±0.002 MPa, and ±0.26 mg, respectively. To confirm reliability of the system, solubility of carbon dioxide in polypropylene (PP) was measured at temperatures of 190, 210, and 240°C. The solubility agreed well with that reported by the authors at temperatures of 190°C and 210°C. The solubilities of carbon dioxide in polycarbonate (PC) and polyamide 6 (PA6) were measured at temperature of 240°C. CO{sub}2 solubilities at 240°C and 10 MPa in PP (0.07 g/g) were the highest followed by PC (0.03 g/g) followed by PA6 (0.025 g/g), and the trends were observed over all pressure ranges. The trend (PP>PC>PA6) seems to be more closely related to the polymer free volume than to specific CO{sub}2-polymer interactions.