Solubility and diffusion behavior of compressed CO2 in polyurethane oligomer

In CO 2 -assisted polyurethane (PU) foaming, the solubility and diffusion coefficient of CO 2 is vitally important to the cell nucleation and growth. This work is aimed at the effect of molecular weights ( M n ) and crosslinking densities ( V e ) on the solubility and diffusion coefficient of CO 2 in PU oligomers. A series of PU oligomers with different M n and V e were synthesized. The solubility and diffusivity of CO 2 in PU oligomers were measured experimentally in the temperature from 80 to 140 °C and with pressures up to 15 MPa. It was shown that the solubility and diffusion coefficients of CO 2 was decreased 20.5 and 21.0%, respectively, with the M n increasing from 5864 to 153,754 g mol −1 at 80 °C, 15 MPa. The solubility and the diffusion coefficient also decreased 11.1 and 38.0% as the V e was increased from 64 to 1493 mol m −3 . Furthermore, the diffusion mechanism of CO 2 in PU oligomers was explored via molecular dynamics simulations. The results indicated that the calculated diffusivity of CO 2 showed the same changing trend as the experimental values, and the smaller M n or crosslinking degree contributed to an increase in fractional free volume and stronger polymer–CO 2 interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47100.