FEM-DEM modeling of thermal conductivity of porous pigmented coatings

In this study, a coupled discrete element-finite element approach was developed to predict the effective thermal properties of model pigmented coating layers. Using this approach the influence of coating structure and pigment and binder characteristics was investigated. It was found that pigments with a broader particle size distribution (PSD) resulted in a higher effective thermal conductivity of the coating layer due to the denser coating structure formed by the pigments. Furthermore, the predicted effective thermal conductivities of the coating layers were found to increase with pigment morphology changing from spherical, to needle-like, and to platy. The effective thermal conductivity of the coating layer increased with the increase in the binder content up to the critical pigment volume concentration (CPVC), but declined when the binder content was higher than CPVC. Lastly, it was found that an empirical equation; keff=A(1-φv)3kpφpklφl, where kp and kl are the thermal conductivities of pigment and latex, and φp, φl, and φv are the volume fractions of pigment, latex, and voids respectively, can be used to estimate the effective thermal conductivity of the coating layer in good agreement with the FEM-DEM simulation results.