Gaskets
Foam gaskets
A foam gasket is a soft cellular sheet, rubber sponge or urethane foam, cut to the outline of a lid, door, panel or housing so it seals dust, water, air or light at low closing force. The usual choices are closed-cell neoprene, EPDM or blended sponge for enclosures and weather, closed-cell silicone sponge for heat and cold, and PORON® microcellular urethane where the gasket must not take a set. Closed-cell sheet keeps water out, while open-cell foam breathes and takes water in. Conquest Seal cuts sponge and urethane foam gaskets to your drawing on our waterjet in Orange, California, plain or with adhesive backing.
- Family
- Cellular rubber (sponge) and urethane foam
- Cell structure
- Closed cell seals water; open cell breathes
- Main choices
- Neoprene, EPDM and blended sponge; silicone sponge; PORON urethane
- Callouts
- ASTM D1056 grades; SAE AMS3195 and AMS3196; PORON grade numbers
- Adhesive
- Pressure-sensitive adhesive on one face, cut with the liner on
- Product
- Sheet gaskets cut to your drawing on our waterjet in Orange, California
Open cell or closed cell
The first question on any foam gasket is whether the cells connect. In closed-cell sheet each cell is sealed, so the gasket does not wick water through itself and seals against rain, wash-down and dust once it is compressed. In open-cell foam the cells connect, so the sheet breathes and soaks up liquid; it cushions, damps and blocks dust and light, but it is not a water seal. ASTM D1056 writes the difference into the callout: Type 1 is open cell and Type 2 is closed cell [S1, S2].
Most enclosure, lid and panel gaskets are closed-cell sponge. Open-cell foam earns its place in cushions, acoustic pads and breathable seals, and on the medical foam gasket page several of the maker-tested foams are open cell.
The foam gasket materials compared
Each material below has its own page with the cited temperature range, thicknesses and callouts. The table is the short form, in our words from those pages' sources; the maker's sheet for the grade on your print governs.
| Material | Cells | Chosen for | Watch for |
|---|---|---|---|
| Closed-cell neoprene, EPDM and blended sponge | Closed (ASTM D1056 Type 2) | Enclosure, door, lid and panel seals against weather and dust at low bolt load; neoprene for moderate oil, EPDM outdoors, nitrile for oil mist | Not a pressure seal; EPDM is not for oils |
| Silicone sponge | Closed (SAE AMS3195 medium, AMS3196 firm) | A wide temperature span, ozone and sunlight; ovens, lighting, outdoor enclosures and aircraft interior panels | Not an oil or fuel sheet |
| PORON microcellular urethane | Very fine, uniform cells | Thin gaskets and pads that must keep their thickness for years: displays, keypads, electronics enclosures and battery packs | The heat limit is on the grade's sheet; strongly polar solvents swell urethane [S4] |
| Open-cell urethane and silicone foam | Open | Cushions, acoustic and vibration pads, dust and light seals, breathable pads | Takes up water; not a water seal on its own |
Compression set, the figure that decides a foam gasket
A foam gasket seals only while it pushes back against the parts it sits between. Compression set measures how much of an imposed squeeze a material fails to recover after it has been held compressed, usually at an elevated temperature, so a low figure means a gasket that still seals after years under a lid. Rogers names compression set resistance as a leading feature of its PORON urethane [S3]. ASTM D1056 carries compression set as a suffix requirement on a sponge callout [S2], and the PORON Medical sheet reports it by ASTM D3574 [S4]. Compare two grades only on the same test method and temperature, because figures from different methods are not comparable.
Firmness and closing force
A soft foam seals an uneven or flimsy cover that a firm one would hold open, while a firm foam resists a latched door that would crush a soft one. ASTM D1056 grades sponge by compression deflection, the pressure needed to squeeze the sheet by 25 percent of its thickness, and the last digit of the callout is that grade [S2]. Silicone sponge is named by AMS3195 for the medium grade and AMS3196 for the firm grade [S5, S7], and PORON by the Rogers grade number, which sets density and firmness [S3]. Match the firmness to the force the cover can apply, and name it on the print.
Adhesive backing
Most foam gaskets are ordered with a pressure-sensitive adhesive laminated to one face by the sheet maker, so the cut part peels off its liner and stays put on the door or lid. The adhesive only holds the gasket in place; the compressed foam does the sealing. Silicone sponge is usually laminated with a silicone adhesive or an acrylic-silicone combination [S6]. The adhesive-backed gasket page covers the adhesive families and what to name on the print.
How foam gaskets are cut
Sheet gaskets are cut to your drawing on our waterjet in Orange, California, closed-cell sponge and open-cell foam alike, with no die to build, so a prototype and a production run go through the same setup. Thick foam is where the waterjet earns its place: on thick sheet a steel-rule die can leave the edge concave, while the jet cuts it clean and square [S8]. Adhesive-backed sheet is cut with the liner on. The custom gaskets page covers the process and the file formats.
What to send for a foam gasket quote
A foam gasket is quoted from the drawing and the material callout. These are the items that settle the quote without a round of questions.
- The drawing. A DXF, DWG or PDF of the outline, or a photo of the part beside a ruler if no file exists.
- The material. The callout if the print has one (an ASTM D1056 grade such as 2C2, AMS3195 or AMS3196, or a PORON grade number), or the material and the firmness wanted.
- The thickness. As the print states it, in inches or millimeters.
- The adhesive. Yes or no, which face, and the tape number if the print names one.
- The service. What the gasket keeps out (water, dust, air, light), the temperature, and anything it touches such as oil or cleaners.
- The quantity. The order quantity now and the annual usage if it repeats.
- The paperwork. A certificate of conformance ships with every order; say if the program also needs the sheet maker's certification.
Related pages
Frequently asked
What is foam gasket material?
A soft cellular sheet, either rubber sponge (neoprene, EPDM, nitrile, silicone or a blend) or urethane foam, that seals at low closing force. It is cut to the outline of the cover, door or panel it seals.
Is closed-cell foam waterproof?
Closed-cell sponge does not wick water through its cells, so a compressed closed-cell gasket seals against water and weather. Open-cell foam takes water in and is not a water seal on its own.
What is compression set?
The share of a squeeze a material fails to recover after being held compressed, usually hot. A low figure means the gasket keeps sealing after years under load; compare grades only on the same test method.
Which foam should a gasket be made from?
Closed-cell neoprene, EPDM or blended sponge for most enclosures and weather seals, silicone sponge for heat and cold, and PORON urethane for thin gaskets that must not take a set. The print or your engineering names the grade.
Can a foam gasket hold pressure?
Not much. Foam and sponge seal against weather, dust, light and low-pressure air at light closing force; a bolted flange with pressure behind it needs solid sheet.
Can foam gaskets come with adhesive?
Yes. The sheet maker laminates a pressure-sensitive adhesive to one face, and the gasket is cut with the liner on so it peels and places. Silicone foam takes a silicone or acrylic-silicone adhesive.
Sources
- [S1] ASTM D1056: Standard Specification for Flexible Cellular Materials: Sponge or Expanded Rubber, D1056-20, read 2026-09-25.
- [S2] ASTM D1056 summary (type, class and grade table), Atlantic Gasket Corporation, read 2026-09-25.
- [S3] PORON 4701-30 Polyurethane, Rogers Corporation, read 2026-09-25.
- [S4] PORON Medical Urethanes, Soft Cushioning and Soft Supporting typical physical properties, publication 10-017, Rogers Corporation, 0315, read 2026-09-25.
- [S5] SAE AMS3195: Silicone Rubber Sponge, Closed Cell, Medium, read 2026-09-25.
- [S6] Current Listing of Pressure Sensitive Adhesives (SR96), Stockwell Elastomerics, read 2026-09-14.
- [S7] SAE AMS3196: Silicone Rubber Sponge, Closed Cell, Firm, read 2026-09-25.
- [S8] Waterjet Cutting, Stockwell Elastomerics, read 2026-09-24.
Stated in our own words from the sources above; no standard's text or table is reproduced.
PORON is a trademark of Rogers Corporation. No affiliation or endorsement is implied.
Related guides
Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution.
Send the foam gasket drawing and the quantity
Upload a DXF, DWG or PDF with the quote request, or a photo of the part beside a ruler. Add the material or callout, the thickness, whether adhesive backing is wanted and on which face, and the quantity. Gaskets are cut on our waterjet in Orange, California; a Conquest representative replies.
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