Mathematical modelling of simultaneous solvent evaporation and chemical curing in thermoset coatings: A parameter study

A mathematical model, describing the curing behaviour of a two-component, solvent-based, thermoset coating, is used to conduct a parameter study. The model includes curing reactions, solvent intra-film diffusion and evaporation, film gelation, vitrification, and crosslinking. A case study with a polyisocyanate and a polyol in an organic solvent, catalysed by an organotin compound, is selected for analysis. The transient effects on reactant conversion values and solid content of the film of the following parameters are studied: initial solvent concentration and film thickness, wind velocity, and bulk air concentration of solvent. Simulations of solvent evaporation are compared to experimental data from a previous investigation. As part of the parameter study, mechanisms of this complex coating system are discussed.