Custom Gaskets & Sealing Systems: Enclosure, Fluid, IP-Rated & Expansion-Joint Seals

They differ in how they close a gap and how much force they need. A closed-cell foam or sponge gasket has a cellular structure, so it compresses easily and seals at a relatively low closure force, which suits enclosure perimeters, panels and light latches; the closed cell is what keeps water and air from passing through it. A solid rubber gasket has no cells, so it is firmer and needs real bolt or flange force to seal, but it handles high clamp loads and aggressive fluids well, which suits bolted flanges.

The terms sponge and foam are often used interchangeably for cellular rubber; what matters for the spec is the cell type (closed for sealing), the compression-deflection, and the compression set. Send the gap, the available closure force and what you are sealing, and the right form follows.

Start with environment and temperature. For an outdoor enclosure that sees weather, ozone and UV but no oil, EPDM is the default because its weather resistance and low compression set keep the seal alive over years outdoors. If the box also sees some oil or you want a broad general-purpose gasket, neoprene gives moderate oil resistance alongside good weather resistance.

If the enclosure runs hot or cold, or needs a flame rating, silicone is the move because it holds its sealing properties across a much wider temperature span and reaches UL 94 flame ratings on specific grades. The one rule that trips people up: EPDM swells in petroleum oil, so do not put it on an oily flange. Confirm the grade, compression-deflection and any environmental limit against the manufacturer's data sheet, and send the groove and closure force.

It depends on which fluid, because compatibility is chemistry-specific. For broad, moderate oil resistance in general service, neoprene is a common choice. For fuel, oil and a wide range of aggressive chemicals at sustained high temperature, FKM (a fluoroelastomer) is the demanding-duty lead. Where you need fuel and chemical resistance plus silicone's wide temperature span, fluorosilicone fits. For media that attack conventional elastomers entirely, Gore GR ePTFE sheet is broadly chemically inert.

EPDM resists water, weather and many coolants but swells in petroleum oil, so it is the wrong pick for an oily flange even though it is excellent for weather seals. The honest answer is always to check the exact media, concentration and temperature against a chemical-compatibility chart and the grade data sheet before committing; send those details and the elastomer can be matched.

No. An IP rating per IEC 60529 is a property of a complete, tested enclosure, not of a raw gasket material. The two-digit code (the first digit is dust and solids, the second is water) is assigned after the assembled enclosure passes the corresponding ingress test. A gasket is one of several things that lets an enclosure reach a given IP class, but the gasket alone cannot carry the rating, the result depends on the groove design, the closure force, the housing, the fasteners and any vents as well.

The right framing is that H-O converts gaskets that support an enclosure's IP claim, using weather-durable, recoverable, low-set materials with a controlled compression-deflection so the groove can be designed for a repeatable seal. If you tell us the target IP class and the groove geometry, we will point you at a family and a compression plan to support it, but the rating is earned by the tested enclosure.

Most closed-cell foam and sponge gaskets seal best within a working-compression band, often somewhere around 25 to 50 percent of their thickness, though the exact window is grade-specific and set by the compression-deflection curve, so always confirm it on the data sheet.

The logic is in the working-window calculator on this page: too little compression leaves the gasket on its soft toe, where it has not closed the gap or built a sealing line; too much pushes it into the densification region, where the stress climbs steeply, the closure force gets high, and the material is more likely to take a fast compression set.

The design target is to land in the middle of the working window across the whole perimeter at the assembly's minimum clamp condition, accounting for tolerance stack-up. Solid rubber gaskets work differently, sealed by clamp stress at a flange rather than a percent-compression window. Send the gap, the tolerance and the closure force, and the thickness and material can be sized.

Because a gasket that takes a permanent set relaxes its sealing force and eventually leaks. Compression set is the permanent thickness a material loses after being held compressed and then released, measured per ASTM D395 (and the cellular-rubber procedures in ASTM D1056). A gasket seals by pushing back against the mating surfaces; as it sets, it thins, the contact pressure drops, and a leak path can open, especially after temperature cycling or long static compression.

This is why EPDM and silicone are specified for low compression set in long-life enclosure and IP seals, why cork-rubber is chosen where very low creep is needed in a thin compressed gasket, and why an over-compressed gasket (driven past its working window) fails sooner. Call out the service life, the temperature, and the duration of compression so the set behavior can be checked against the grade data sheet.

They describe enclosure environmental protection in two different systems. IEC 60529 IP codes are an international two-digit scheme: the first digit rates protection against solids and dust, the second against water, so IP65 means dust-tight and protected against water jets. UL 50E enclosure types are the North American scheme that rates enclosures as Type 1, 3R, 4, 4X and so on, bundling protection against dust, water, ice and corrosion into named types for specific use environments.

They overlap but do not map one-to-one, because the test conditions differ. For a gasket, both come down to the same job: a continuous, recoverable, weather-durable seal compressed correctly in a defined groove. Tell us which rating system and target the product must meet, and the gasket family and compression plan can be chosen to support it, remembering that the rating belongs to the tested enclosure.

A pressure-equalization vent is a small breathable element, typically an expanded-PTFE membrane such as Gore ePTFE, that lets air pass through the enclosure wall to balance internal and external pressure while still blocking liquid water and dust. A well-sealed enclosure has a hidden problem: as it heats and cools, the air inside expands and contracts, which builds a pressure difference that stresses the seals and can pull moisture past them or deform the housing.

A vent relieves that pressure difference without breaking the seal, because the membrane is permeable to air but not to liquid or particulate. It is the complement to the perimeter gasket: the gasket keeps weather out, and the vent keeps the box from becoming a pressure vessel. H-O the membrane into vent disks and patches that pair with the perimeter seal.

Confirm the membrane grade and airflow against the manufacturer's data.

An expansion-joint seal has to stay in contact and recover as the gap opens and closes with thermal and structural movement, so it is sized to the joint's movement range rather than to a single gap.

Compressible closed-cell fillers in weather-durable elastomers, solid or sponge EPDM and neoprene, are common because they recover across the movement and resist weather; butyl tape gives a watertight, no-cure seal at laps and transitions where a conforming peel-and-place tape is the right form; and cork-rubber serves stiff, low-creep joint and bearing gaskets under load.

The key spec input is the movement range, the maximum and minimum gap the seal must bridge while staying compressed enough to seal, plus the weather exposure. Send the joint width, the movement range and the exposure, and the filler material, profile and thickness can be matched, then confirmed against the grade data sheet.

Often yes, for assembly, but it is a separate decision from the seal itself. A pressure-sensitive adhesive backing holds the gasket in place on one mating surface during assembly so it does not shift or fall out before the lid closes, which matters most for perimeter gaskets that wrap a groove or a vertical face. The adhesive is for placement, not for sealing, the seal is made by compression, so the adhesive side is chosen by which surface the gasket should stay on during build.

The adhesive system also has to suit the substrate and the service temperature, and for low-surface-energy plastics a specialized adhesive may be needed. H-O laminates the adhesive, supplies it on a release liner with pull tabs if useful, and kiss-cuts the part for peel-and-place. Tell us the substrate, the service temperature and how the part is installed, and the adhesive and liner can be specified.

Six things move a recommendation from a guess to a real direction: what you are sealing (dust and water, a specific fluid, movement, or venting), the media and chemistry for a fluid seal, the operating temperature, the available closure force and the gap to close, any IP or enclosure-type or flame target, and the part geometry or a drawing.

Add the adhesive and liner needs and the prototype and annual volume, and engineering can match a family, a grade direction and a converting approach, then confirm the grade-level values against the manufacturer's data sheet and a compatibility chart.

The "What to send H-O" box below lists these. If you only know the symptom, "this enclosure leaks in the rain," "this flange weeps oil," that is a fine starting point too; describe it and we will work back to the spec.

H-O is a precision converter, not a raw-material producer. We do not extrude or mold the rubber, foam and membrane; we buy sheet, slab and roll stock from the material manufacturers and convert it to your drawing, by die-cutting, kiss-cutting, laser and waterjet cutting, adhesive lamination, slitting and kitting, with material traceability and lot-level data-sheet records.

Every gasket and sealing part is made-to-order; we do not carry finished parts in stock and we do not advertise a no-minimum policy, though prototype quantities through full production runs are equally welcome and the minimum varies by material and part.

Prototype and production timing is summarized in the process strip near the top of the page and on the quote form. Send your drawing or describe the joint and what it must seal through the form below for a specific quote.