Water-borne paints and coatings are dispersions of sub-micrometer polymer particles. Paints and inks are multi component mixtures that include polymer particles, also called filmformers or binders, and a variety of surfactants, processing aids, pigments and sometimes a small amount of solvent.
Paints form films by a process called coalescence where first the water evaporates drawing the binder particles together and then fusing them into irreversibly bound networked structures. All paints that use synthetic polymers such as acrylic, vinyl acrylic (PVA), styrene acrylic, etc. as binders are emulsion or latex coatings.
Some paints cure by oxidative crosslinking, where exposure to oxygen in the air starts a process that hardens the binder component, an example would be alkyd enamels. Paints that need to dry before curing can require a two-step coating process, examples of these are epoxies and polyurethanes. An alternative means of curing paints particularly for industrial purposes is by UV. In UV cured paints, the solvent is evaporated first, and hardening is then initiated by ultraviolet light.
Adhesive properties, long term aging, film-formation or lack of defects in the final film-formation are important product performance issues.
Malvern’s range of easy to use particle size, zeta potential, rheological and imaging instrumentation can be used in the study of paints, inks and coatings. These systems and our industry and application knowledge can be used to:
- Characterize the size and polydispersity of the water borne dispersion.
- Determine charge of the film-former and the interfacial interactions of the water soluble components in the product.
- Determine charge of the substrate and then optimize the charge of the coating for improved adhesive properties.
- Determine viscosity characteristics that influence the coalescence properties of the coatings.
- Rheological measurements to characterize fluid flow which is relevant to spreading and leveling of coatings.