The phase behavior of crosslinked polyisoprene rubber (PIR) in CO2 at temperatures ranging from 293 to 453 K and pressures ranging from 0.1 to 20 MPa were investigated. Visual swelling measurements based on the sample dimensions were performed using a high-pressure view cell. The change of the degree of swelling with time provided a diffusion coefficient of CO2 in crosslinked PIR. The solubility measurements were carried out by using a magnetic suspension balance (MSB) method. The weight change of the sample in CO, under elevated pressure and temperature was converted to solubility taking the buoyancy effect and the degree of swelling into account: the degree of swelling was derived both from the visual swelling measurement and from theoretical estimation on the basis of the Sanchez-Lacombe equation of state. The solubility from the two methods was in good agreement with each other in the range from 8 to 13 MPa. (c) 2005 Elsevier B.V. All rights reserved.