Molecular Dynamics Simulation of the Compatibility Between Supercritical Carbon Dioxide and Coating Resins Assisted by Co-Solvents

Abstract

The use of supercritical carbon dioxide (ScCO2) as a replacement for volatile organic solvents in coatings has the potential to reduce air pollution. This paper presents the findings of a molecular dynamics simulation study investigating the dissolution behavior of polyvinylidene fluoride (PVDF) in ScCO2 assisted by five co-solvents. On the basis of solubility parameters, interaction binding energy, and radial distribution functions, the impacts of temperature, pressure, and co-solvents on the compatibility of ScCO2 and PVDF were investigated at the microscopic level. The simulation results demonstrated that low-temperature and high-pressure conditions facilitate the dissolution of PVDF in ScCO2, where the optimal conditions are 308.15 K and 16 MPa. The enhancement of the solubility performance of ScCO2 slowed down with increasing pressure, but was more sensitive to changes in temperature. The weak attraction between PVDF and ScCO2 was synergized by van der Waals and electrostatic forces, making it challenging to achieve complete and homogeneous mixing. The use of co-solvents with strong polarity can enhance the solvent system’s solubility. Ethanol and 2-butoxy-1-ethanol have obvious solubilizing abilities due to the hydrogen bond donors, which can generate hydrogen bonding interactions with ScCO2, increase the polarity of the solvent system, and promote the compatibility of ScCO2 with PVDF.