Closed Cell Gasket

When a water tight seal is required, a closed cell gasket material should be used. Typically when the term "closed cell" is used it is in reference to expanded or blown materials rather than solid material. The closed cell refers to a cell structure where each cell is fully enclosed, much like tiny balloons. When a closed cell gasket is compressed, the walls of the cell will deform, much like a balloon would. This is why compression of closed cell products should be limited (typically to no more that 50%) to keep from bursting cells. This is in contrast to open cell products where the cells are open to each other. When an open cell gasket is compressed, the air within the cells is squeezed out.

Dust Gaskets
There are many materials that can perform the duty of dust sealing. The degree of sealing can vary and should be considered. As an example, a clean room dust gasket may have a "higher" level sealing than an industrial enclosure gasket, because the ingress of dust in a clean room can be catastrophic to the process in a clean room versus just a bit of dirt in the industrial application. One of the primary concerns for a dust gasket is to ensure the gasket will not take a compression set. If a door gasket takes a set, it could leave gaps over time, hence defeating the purpose of the gasket. In general, materials that have a high level of filler (used to make products less expensive), will take a compression set more readily.

UL94 Gasket
A UL94 gasket is one that must meet the Underwriter Laboratories flame rating UL-94. The flame ratings are used to identify how materials will perform when exposed to flames. The materials are classified base on how they support a flame. For example, a material that meets the more aggressive UL 94 V0 rating will self extinguish within 10 seconds and have no drips when a vertical swatch is exposed to a flame. When a device is required to go through UL testing, the gasket and pad materials are evaluated as well. Providing the material's datasheet that calls out the UL rating is often sufficient.

Die Cut Gaskets
Gaskets and pads can be cut in a variety of ways. The size of the parts, the type of material and the quantities are factored in to determine the most cost effective method to produce parts. The most common die for elastomer cutting is a steel rule die. This is where a CAD file is used to program a laser cutter, the laser burns the part geometry into engineered wood. Steel ruling (steel strip with a bladed edge) is pressed through the laser cut slots. More complex designs may require a solid steel die, where the blades are machined into a solid block of steel. The dies can be mounted to high speed presses or manually operated press for lower volumes. Stockwell is equipped to handle low to mid-volume runs (parts in thousands, single runs, not millions) using high speed Preco semi-automatic die cutting presses, auto-feed CNC large bed presses or a variety of beam presses.

Kiss Cut Gaskets
A subset of die cut gaskets is the kiss cut (or kisscut) gasket. This is when the die, for a gasket with adhesive on one side, is punched through the material but not all the way through the adhesive liner. The adhesive liner remains intact, allowing the parts to be rolled up on the liner. This process is favorable for manufacturing because the reel or roll of parts can be hung in a manufacturing cell. The parts are then peeled off the liner as opposed to the liner being peeled off of the parts.

Waterjet Cut Gaskets
Stockwell Elastomerics utilizes its three waterjet cutting units to cut tight tolerance and low volume parts. The closed loop servo drive system allows for very accurate cutting. As with all elastomers, the cut tolerances are larger than standard metal cut tolerances, because elastomers are dynamic when they are being cut due to being soft and pliant. For low volume parts there is an immediate savings because there is no tooling charge if a CAD file is provided.

Sponge EPDM Gaskets
EPDM (Ethylene, Propylene, Diene, Methylene) is commonly specified for outdoor gasketing applications. This is due to EPDM's excellent weatherability, and specifically its resistance to UV, ozone and oxidation. The closed cell structure minimizes water absorption which makes it a good material for enclosure gaskets needing occasional resistance to moisture and indirect water spray. EPDM sponges are available in various firmnesses from very soft to firm. EPDM gaskets are not recommended where they may come in contact petroleum based oils and certain chemical (call for specific information).

Contact Stockwell Elastomerics, Inc.
Contact Us for further assistance with custom gaskets such as waterjet cut gaskets, closed cell gaskets, dust gaskets, UL94 gaskets, die cut gaskets, kiss cut gaskets and sponge EPDM gaskets.