“Considerations for Selecting a Dome Coating”
With hundreds of dome coating options available on the market, selecting the right dome coating for your application can seem like a daunting task. When selecting the best coating for your application, it is important to consider five main criteria: viscosity, substrate flexibility, substrate adhesion, hardness, and environmental durability.
- Viscosity. How thick does the coating need to be? Decorative coatings are clear and usually thin. Dome coatings have curved domes, which optically magnify and enhance the appearance of a label. Higher-viscosity, thicker resins generally produce taller domes.
- Substrate Flexibility. Flexible substrates, like thin polyester labels, paper, or soft plastics, may require careful selection of coating and enhanced curing equipment. Flexible substrates may bow or warp when thick coatings cure. Soft coatings shrink less and are designed to reduce or eliminate warpage during cure. Rigid substrates don’t bend when stressed, so they can be coated with all of the products.
- Substrate Adhesion. Individual formulations may have excellent adhesion to some inks (or substrates) and little adhesion to others. The right coating should have good adhesion. Adhesion should be tested after product lifetime testing, as well as after cure. Inks and substrates from second source suppliers may improve or worsen adhesion. Some plastics require surface treatment to enhance adhesion.
- Hardness. Both soft and hard coatings can be scratch resistant. Hard coatings resist scratching because of their hardness. Soft coatings resist scratching because they momentarily dent and then spring back when the scratching object is withdrawn. Hard coatings are measured on the D-hardness scale. Soft coatings are measured on the hardness scale. On both scales, higher numbers imply harder coatings.
- Environmental Durability. Coatings should be lifetime tested on your product. Some properties, like UV weatherability, provide a relative guideline to distinguish endurance of clarity and durability among the available products offered.