In this paper

the curing extent of polymer film and the reaction speed constant of the crosslinking and curing in the acrylic polyurethane coating system were determined by FTIR analysis. The film-formation process of this coating system was simply treated as that of a binary polymer-solvent system. On the basis of Vrentas-Duda free volume theory

the diffusion coefficient of solvent and the reaction extent of film-formation polymer are correlated by introducing Di-Benedetto equation

and the self and mutual diffusion coefficients of the solvent in this system were calculated.It was shown that the diffusion coefficients of the solvent in such a thermosetting coating were dependent on solvent concentration and drying time.