Protective and Decorative Dome Coating
Dome coating is often associated with decorative, novelty items such as pens, lapel pins, name plates and logo stickers. The coating forms a protective layer over the items, but generally the main purpose is the glossy, raised appearance which can magnify the image below it. In other applications the coating is primarily protective and the appearance is of less concern.
The coating selection process is similar for both protective and decorative coatings. The main points to consider in selecting a dome coating are:
Processing choices – Today there are a variety of processing choices available including: a) two component reactive systems, b) solvent based systems, and c) UV Curable systems. Two component reactive systems require mixing, followed by de-airing. Solvent based systems can create difficulties with the health and safety and workplace handling.
UV Curable dome coating requires UV cure equipment which can be costly. However, equipment choices have expanded and become less costly due to developments in dome coating chemistry. Historically, fairly high intensity UV light was required to cure the surface of the coating to a tack free dry surface. Recent advances in UV curable dome coating materials now offer a tack free finished appearance with low intensity UV light (which also helps minimize shrinkage and overheating during cure).
These advances expand the selection of lamps that are appropriate for coating. The cure process can be tailored by choosing equipment that will provide the optimal time vs intensity cure model for the coating and the expected production requirements.
Parts –What are the parts made of? A common dome coating application is dome coating a logo. The logo may be a screen printed paint or a sticker… so consider, what material does the coating need to bond to? This will help to determine a product with good adhesion to the substrate. Will the coating material in its liquid form attack the ink or artwork it is supposed to protect?
Is the part flexible? If the end item requires flexing, ideally the coating should be flexible as well to increase durability. If the end item is very thin or very flexible, further considerations into dome depth, shrinkage and hardness of the coating will be considered to ensure the part doesn’t curl up on the edges.
Purpose – Like all scientists, adhesive manufacturers like to hear the numbers – what are the temperature requirements, chemical exposure times & concentrations etc… But, it is generally best to begin the conversation with the purpose – the purpose of your assembly provides so much more information. For example will it be exposed to the elements outdoors on a vehicle badge, going through a dishwasher or even more extreme, in a subsea application?
For further help and advice please contact Permabond.