Thermal characterisation of solvent-free epoxy coatings
Rheology and kinetics are a pair of indispensable attributes in defining thermally reactive polymer coatings and paints. For a new work work, cure paths of volatile organic compound-free epoxy powder coatings, under heat, were characterized by viscoelastic and kinetic techniques.
The essential rheological meanings of the gel point, the minimum complex viscosity, and the shear moduli from dynamic mechanical analysis curves were elucidated from applied formulation perspectives. Meanwhile, the maximum cure reaction rate and the peak temperature from differential scanning calorimetry exothermic profiles were quantitatively interpreted using primarily the extent of cure along with viscoelastic data. Vitrification and devitrification during cure were observed for high glass transition (Tg) epoxy formulations, unless a fast rate of heating was employed to a high enough temperature.
Strong insights for product development
Thorough and complete cure description provides strong insights for product development, allowing flow and cure properties to be balanced for optimal line performance. The consolidated approach is applicable to nearly all B-staged thermosetting systems of 100% solids including conditioned prepregs and a variety of adhesives per applications, as well as direct-to-metal primers or topcoats per functions.
The study can be found in Journal of Coatings Technology and Research, Volume 17, 2020.