The Waterborne Symposium

Abstract
Thermal Characterization of Solvent-Free Epoxy Coatings by Rheology and Kinetics Combined

Rheology and kinetics are a pair of indispensable attributes to define thermally reactive coatings and paints.  In this work, VOCs-free epoxy coating cure paths under heat are characterized via viscoelastic and kinetical behaviors with functional powder coating formulations as examples.  As a result, what the gel point, the minimal complex viscosity (h*min) and the shear moduli G’ & G’’ from rheological curves, and as well the maximal cure rate (ȧmax or damax/dt) and the peak temperature (Tpeak) out of differential scanning calorimetry (DSC) exothermic profiles essentially mean when it comes to an application-oriented formulation are quantitatively interpreted with respect to dynamic modulus, viscosity, and the instant extent of cure (a).  Events of vitrification and de-vitrification in a cure process are pertinently observable for high glass transition temperature (Tg) epoxy matrix coatings unless a fast enough heating rate (b) to a high enough temperature is employed.  Complete cure description provides strong insights into product developments allowing particular flow and cure properties balanced to boost line performance, applicable to nearly all B-staged thermosetting systems of 100% solids such as conditioned prepregs, adhesives and underfills besides epoxy-based liquid, e-coat, and powder primers or overcoats.