Guest Author: Mike Burris, Product Development – CGR Products
Enclosure gaskets are mechanical parts used to provide weatherproof seals on electrical enclosures and their doors. The typical method of attaching the gaskets is by means of a chemical fastener such as pressure sensitive adhesives (PSA). The mating surfaces are often irregular, making it hard to get a continuous seal. In order to protect the sensitive electronic equipment inside the enclosure, a properly selected and manufactured gasket is critical. The enclosures can be used indoors or outdoors; therefore, a properly selected material and design are essential to ensure proper performance and long life. Generally, gaskets are used to seal out dust, dirt, water, Electromagnetic Interference (EMI), and Radio Frequency (RFI). Gaskets can also be used to dissipate vibration.
Strip gasketing has been around a long time. Supplied in rolls, the manufacturers of the enclosures adhere strips of compressible foam to the enclosure surface to be sealed. One side of the foam will have a pressure sensitive adhesive designed to adhere to the enclosure structure. The corners are not completely sealed due to the non-continuous strip design. This method is the most economical but the corners are areas of concern for some applications.
Fold Out/ Dovetail Gasket
In instances of very large enclosures, high volumes, or where the design does not allow for strip gaskets, a fold-out or dovetail gasket may be an option. The fold-out gasket allows the die cut to be expanded to its final shape, eliminating the center scrap. A dovetail gasket works in a similar fashion, except the corners are mitered and fit together like a jigsaw puzzle. The design of the enclosure and level of ingress protection needed will determine if this type of gasket is suitable.
Armacell EnsoLite and Monarch elastomeric foams are the most common and affordable materials used for enclosure gaskets and seals. These materials are available in closed-cell, semi-closed crushed foam, and foam blends, with and without pressure sensitive adhesives (applied by a foam converter). The key to choosing a gasket material is defining the environment in which it must perform. One must consider temperature / thermal management requirements, UV and Ozone exposure, EMI / RFI resistance, just to name a few. The following is a list of the most common elastomeric materials available that carry UL Listings and ASTM listings:
- Nitrile (NBR)
- Styrene Butadiene Rubber (SBR)
- Ethylene Propylene (EPDM)
- Neoprene (CR)
- PVC/NBR Blends
- PVC/NBR/CR Blends
- Epichlorohydrin (ECH)
- EPDM/CR/SBR Blends