Drying behavior of polymer solution containing two volatile solvents

A study on the drying of thin layers of polymer solution containing two volatile solvents is performed through experiments and numerical simulation. In the experiments, the individual drying rate of each solvent as well as the overall drying rate is obtained. The initial composition and the thickness of a sample are varied in order to examine their effects on the drying characteristics. Moreover, simulation is performed by solving a pair of diffusion equations for each solvent together with a heat balance equation. The diffusivity and the vapor pressure of solvents necessary for the simulation are estimated using free-volume theory of Vrentas and Duda and the Flory-Huggins equation, respectively. The results of simulation show qualitative agreement with experiments, while apparent mass transfer rate in the film is smaller than that estimated from diffusivity data found in the literature. The reason of underestimation is a future subject.