Accurate measurement of viscoelastic parameters

If organic coatings are exposed to moisture or water, their adhesion to the substrate is changed. It is particularly important to know their viscoelastic parameters under such conditions to be able to develop specific property profiles for coatings systems. A new sample cell for a dynamic thermoanalysis (DMTA) apparatus enables changes in glass transition temperature caused by water to be determined. Comparison of these data with conventionally determined adhesion strength shows: depending on the coating/substrate system, adhesion improves if plasticisation by water has lead to increased segment mobility. If the water is concentrated in the boundary layer at the substrate, adhesion is reduced.