Heat and mass transfer with polycondensation in resin film during drying

In a drying process of dielectric resin films coated on electric conductive substances, phenomena such as polymerization of monomers, by-products yiel d, shrinkage and stress generation; take place simultaneously in addition t o heat and mass transfer. For the enhancement of the drying with high effic iency and high quality, it is important to understand the drying mechanism. In this paper, the characteristics of heat and mass transfer in the resin film including polycondensation reaction are presented. The apparent drying rate of polyamideimide varnish films was measured in two different heating modes of radiation and convection. The reaction rate of polycondensation w as analyzed both by the thermogravimetry and the differential scanning calo rimetry. The apparent drying rate began to drop remarkably when the reactio n rate became significant. It implies that the diffusion of the solvent is inhibited by skinning at the surface. Applying the Vrentas/Duda free-volume diffusion model to the prediction of diffusivity, the heat and mass transf er in the resin film were analyzed theoretically with a reasonable accuracy .