The World of Surface Coatings is Centered Around the Glass Transition Temperature, But Which One? Part 2

By Greg Curtzwiler, Mark Early, Diana Gottschalk, Christina Konecki, Robert Peterson, Steven Wand, James W. Rawlins

As was discussed in Part I of this article
[CoatingsTech, Vol. 11 (8) 28-38 (August 2014)], polymeric materials are employed in a wide variety of applications. Whether the desired performance is a mechanical response, specific permeability, chemical reactivity, or general response to any given stimuli, the target properties are strongly affected by the molecular dynamics of all blended materials and reactants. The molecular dynamics of amorphous materials are controlled by the resulting glass transition temperature (T_g).

This two-part article reviews the importance of T_g in polymeric coatings and emphasizes the shifting nature of a material’s T_g throughout the service lifetime. In attempting to simplify a complex combination of material dynamics, a polymer’s T_g has often been utilized as a single value parameter throughout history. While correlations exist between the T_g and many important material properties, a single T_g value does not communicate the multifaceted material dynamics involved in formulation, application, film formation, cure, or in-service use.