Gasket material

Closed-Cell Sponge Rubber Gasket Material

Closed-cell sponge is expanded rubber whose cells do not connect, so it seals against water, dust and air at low bolt load. It is the enclosure, lid and panel gasket sheet: neoprene, EPDM, nitrile and neoprene/EPDM blends, graded under ASTM D1056, and cut to your drawing on our waterjet.

Request a quote in Closed-Cell Sponge RubberAll gasket materials
Family
Cellular rubber, closed cell
Temperature
-40 C to 121 C (-40 F to 250 F) on the maker's sheet for a neoprene/EPDM blend; other grades per their sheet
Designations
ASTM D1056 Type 2 grades, e.g. 2A1, 2C1
Product
Sheet gaskets waterjet-cut to your drawing in Orange, California

Figures are the cited maker or standards values; the sheet datasheet and your application govern the final choice.

Every common gasket sheet material is quick for us to source, and we cut it to your print on our waterjet. The other sheet materials are on the waterjet-cut gaskets page.

What closed-cell sponge seals

Closed-cell sponge compresses easily and springs back, so it takes up gaps between stamped covers, doors, lids and panels that a solid sheet would bridge only under heavy bolting. Because the cells are sealed, the sheet does not wick water the way open-cell foam does. That makes it the usual choice for weather seals, dust seals, vibration pads and enclosure gaskets where the load is a latch or a few screws, not a flange.

Read the ASTM D1056 callout on the print before you pick a sheet. The first digit is the cell type, the letter is the class and the last digit is the firmness grade [S3]. The class is a performance requirement, not a polymer: class C asks for oil resistance with medium mass change [S3]; Monmouth's neoprene/EPDM DK blend, for example, is graded 2C1 to 2C5 [S4]. A print that says 2C2 wants closed-cell sponge that meets class C at 5 to 9 psi compression deflection. A 2A1 wants a soft sponge with no oil requirement; Monmouth's 100 percent EPDM P191HD is one example [S5].

Neoprene, EPDM or blend

Neoprene sponge tolerates moderate oil and weather. EPDM sponge is the outdoor and ozone choice where no oil is present; one maker's 100 percent EPDM sponge is rated excellent for UV and ozone [S5]. Blended sponge is available UL-recognized, and the neoprene/EPDM DK series that carries those recognitions is graded class C, not A [S4]. Nitrile sponge is the one to name when the gasket sees oil mist or fuel vapor. For high or low temperature, silicone sponge takes over.

For a side-by-side view of closed-cell sponge, silicone sponge, PORON® urethane and open-cell foam, see the foam gaskets page.

Specifications

Closed-Cell Sponge Rubber specifications

Values as published by the cited sources; [Sn] refers to the source list below
PropertyValue (in / mm, C / F as stated)Source
Cell structureClosed cell is ASTM D1056 Type 2; open cell is Type 1[S4, S1]
ClassSet by performance, not by polymer: A, no petroleum-oil resistance required; B, oil resistance with low mass change; C, oil resistance with medium mass change; D, extreme temperature resistance. For example, Monmouth's 100 percent EPDM P191HD is graded 2A1 and its neoprene/EPDM DK blend 2C1 to 2C5[S4, S6, S5]
FirmnessThe grade digit is the compression deflection at 25 percent: grade 0 is 0 to 2 psi, grade 1 is 2 to 5 psi, grade 2 is 5 to 9 psi, grade 3 is 9 to 13 psi, grade 4 is 13 to 17 psi and grade 5 is 17 to 25 psi, as the sponge maker's explainer gives them for the D1056-14 edition[S3]
Example grade, blended spongeMonmouth Rubber & Plastics DK1111, neoprene/EPDM blend: ASTM D1056 2C1, density 6 plus or minus 2 pcf, compression deflection 2 to 5 psi[S4]
Example grade, EPDM spongeMonmouth Rubber & Plastics P191HD, 100 percent EPDM: ASTM D1056 2A1 F2, compression deflection 2 to 5 psi[S5]
Temperature, blended sponge-40 C to 121 C (-40 F to 250 F) on the maker's sheet, all five DK grades (2C1 to 2C5)[S4]
Temperature, EPDM and other spongeThe sheet maker's data sheet for the grade governs; makers print different ranges for the same polymer[S5, S6]
ListingsBlended sponge is available UL-recognized: the DK series is recognized to UL 50E, UL 157 and UL 508, and to UL 94 HF-1[S4]
DesignationsASTM D1056 type, class and grade (for example 2A1, 2C2); the standard lists Types 1 and 2, Classes A to D, Grades 0 to 5[S1, S4]

How we cut it

Gaskets are waterjet-cut to your drawing in Orange, California. Send a DXF, DWG or PDF with the thickness, the material or the specification callout, and the quantity. There is no die to build, so a single prototype and a repeat run go through the same setup, and a revision needs only a new file. The sheet comes from the sheet makers we buy from, to the callout on your print; the cutting is ours. Thick sponge is where the waterjet earns its place: a steel-rule die pinches soft cellular sheet and leaves a concave edge, while the jet leaves the edge square. Adhesive-backed sponge is cut with the liner on.

Where Closed-Cell Sponge Rubber is used, and the usual alternatives

The print or the sheet datasheet governs; these are the sheets usually specified instead:

  • Solid neoprene: when the gasket carries a bolted flange load and needs to hold pressure.
  • Silicone sponge: when the enclosure runs hot or cold beyond what neoprene and EPDM sponge tolerate.
  • PORON foam: when a thin, low-compression-set pad is wanted for electronics or displays.
  • Adhesive backing: when the gasket must stay put on a door or lid during assembly.

Related gasket materials: Neoprene Gasket Material, Silicone Sponge Gasket Material, PORON Polyurethane Foam Gasket Material, Adhesive-Backed (PSA, Peel-and-Stick) Gasket Material, Wool Felt Gasket Material. The full index is on the gaskets hub; send the drawing through request a quote.

Frequently asked

What is the difference between closed-cell sponge and foam?

Trade use is loose. In ASTM D1056, sponge or expanded rubber is the material, and Type 2 means closed cell. Both open-cell foam and closed-cell sponge are cut in house on the waterjet.

How do I read a D1056 callout like 2C2?

Type 2 is closed cell; class C is oil resistance with medium mass change; and grade 2 is a compression deflection of 5 to 9 psi at 25 percent. State the callout on the print and the sheet is matched to it.

Can you cut sponge with adhesive on one side?

Yes. Adhesive-backed sponge is cut with the release liner on, so the part arrives ready to peel and place. Say which face gets the adhesive.

How thick can a sponge gasket be?

The thickness depends on the sheet the maker supplies in your grade; name it on the print and it is confirmed on the quote. Thick sponge cuts cleaner on the waterjet than under a die.

Does closed-cell sponge hold pressure?

Not much. Sponge seals against weather, dust and low-pressure air at light bolt load. A flange with pressure behind it wants solid sheet.

Sources

  1. [S1] ASTM D1056-20, Standard Specification for Flexible Cellular Materials: Sponge or Expanded Rubber, https://store.astm.org/d1056-20.html, accessed 2026-09-13.
  2. [S2] ASTM F104-11(2020), Standard Classification System for Nonmetallic Gasket Materials, https://store.astm.org/f0104-11r20.html, accessed 2026-09-13.
  3. [S3] ASTM D 1056 explained, Monmouth Rubber & Plastics Corp. (sponge maker), https://monmouthrubber.com/wp-content/uploads/2016/09/ASTM-D-1056-explained.pdf, accessed 2026-09-25.
  4. [S4] DK series neoprene/EPDM closed-cell sponge, DK1111 to DK5151, physical properties sheet (January 2012), Monmouth Rubber & Plastics Corp., https://monmouthrubber.com/wp-content/uploads/2016/06/UL-Listed-EPDM_NEOPRENE-Closed-Cell-Rubber-Blend-Durafoam-DK-Series-DK111-DK2121-DK3131-DK4141-DK5151.pdf, accessed 2026-09-25.
  5. [S5] P191HD 100% EPDM closed-cell sponge, physical properties chart (November 2010), Monmouth Rubber & Plastics Corp., https://monmouthrubber.com/wp-content/uploads/2016/04/EPDM-Series-Durafoam-P191HD.pdf, accessed 2026-09-25.

PORON is a trademark of Rogers Corporation. Durafoam, in two source links below, is a trademark of Monmouth Rubber & Plastics Corp. No affiliation or endorsement is implied.

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Setting Conquest Seal up as a supplier?

Compliance documents for supplier onboardingQuality and certificationsSecond source for O-rings and sealsStocking and vendor-managed inventorySupplier requirementsVendor consolidation for O-rings, seals and gaskets

Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution.

Send the Closed-Cell Sponge Rubber gasket drawing and the quantity

Upload a DXF, DWG or PDF of the gasket with the quote request, or a photo of the part with a ruler if no drawing exists. Add the sheet thickness, the durometer or grade, the quantity and whether adhesive backing is wanted. Gaskets are cut in our own shop in Orange, California; a Conquest representative replies. Quotes answered within one business day. A person answers (714) 632-9830, Pacific business hours.

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