EVA Gasket

An EVA gasket is a sealing and cushioning part cut from closed-cell foam based on ethylene vinyl acetate. Unlike a rubber gasket it is a foam, not an elastomer: it will not hold pressure, but it compresses under a far lower closing force and fills the irregularities in a face. That single distinction explains most of where an EVA gasket is the right choice and where it is the wrong one.

Where EVA belongs, and where rubber does

An EVA gasket works against dust, moisture, draughts, noise and vibration. Electronic equipment lids, lighting fixtures, appliance panels, in-box divider gaskets and hand-closed covers are its typical places; on joints made from thin sheet metal or plastic, closed by clip or screw rather than by bolt, a rubber gasket stays too firm and strains the lid. Conversely, an EVA gasket should never be used on a joint holding internal pressure, carrying hot fluid, or in contact with oil or solvent. Temperature is limiting too: EVA is a thermoplastic foam, so it softens as temperature rises and thins permanently while held compressed. For sustained heat or a chemical environment, EPDM, NBR or silicone is the right address.

Why closed cell is essential

In sealing, cell structure often decides more than the material's name. In a closed-cell foam the cells are separate from one another; the material does not take up water and does not carry moisture from one face to the other. An open-cell polyurethane foam cut for the same place looks fine at first, then absorbs water and wicks it inward — it becomes a wick, not a gasket. That is why closed-cell EVA or XPE is chosen wherever moisture is involved; open-cell foam is only adequate for dust exclusion and cushioning. Sheets sliced from a thick block carry cut-open cells on the surface; what decides the seal is the flat area the gasket presses against, not the cut edge.

Density, thickness and compression

Density determines how much the gasket resists compression and how much it recovers once the load is removed. Low-density EVA crushes under very little force, but held compressed for a long time it will not return to its original thickness; if the gasket no longer fills the gap after the lid has been opened once, that is usually the reason. High-density EVA recovers better and, in exchange, demands more force to close. Thickness is chosen against the gap in the closed position: the gasket must be somewhat thicker than the gap so that it is partly compressed at assembly. Too thick and it strains the lid, tires the latch and squeezes out; too thin and it never touches the opposing face. Strip width belongs in the decision too: a narrow strip is crushed more under the same force, while a wide one makes the lid harder to close.

Cutting, taping and delivery

EVA gaskets are cut from sheet and roll by steel-rule die, CNC or waterjet. Because the closed-cell structure gives a clean, dust-free edge, thin frame gaskets, punched washers and narrow strips come out cleanly. A steel-rule die is more economical for repeat runs, CNC for low volumes and complex geometry. One face can be supplied with adhesive backing on request; peel the liner and apply directly — a dry, oil-free surface directly affects bond strength. Where a single sheet is not thick enough, material is laminated up to thickness. On visible faces colour is a criterion as well: a black gasket disappears in most places, while white and coloured gaskets are matched to the panel in presentation cases. Dimensions, thickness and colour are set per project; send a drawing or a sample and a sample is cut first, with series production following approval of the fit.