How to Choose Sealing Materials for Harsh Environments
Industrial seals must maintain contact between surfaces exposed to chemicals, process fluids, temperature extremes, and weather, often all at once. No single material performs in every environment. Identify the exposure first, then match the material and construction. Engineered Materials supplies closed-cell foams, solid rubbers, silicones, industrial tapes, and adhesive sealants for sealing and gasketing.
Four Factors That Determine Sealing Material Selection
Chemical exposure: acids, caustics, solvents, and cleaners can degrade rubber and lead to partial failure. Compatibility depends on the compound, concentration, temperature, and duration. ASTM D471 provides a comparative measure of rubber's resistance to liquids.
Fluid exposure: oils, fuels, hydraulic fluids, coolants, and water. Occasional contact differs from continuous immersion: 3M, for example, notes that occasional chemical contact should not harm VHB™ tapes in most applications, but it does not recommend continuous submersion.
Temperature extremes: ratings vary widely. BISCO® 7304 silicone sponge is rated for 450°F, while 3M™ Extreme Sealing Tape is rated for 200°F for long-term use. On adhesive-backed parts, both the material and the adhesive set the limit.
Environmental exposure: UV, ozone, moisture, dust, and thermal cycling. ASTM D1149 evaluates surface ozone cracking.
Materials That Hold a Seal Against UV, Ozone, and Weather
BISCO® silicone foam is rated from -67°F to 392°F, resists UV, ozone, and mechanical fatigue, and recovers quickly after compression. Grades range from ultra-soft BF-2000, which seals with low closure force, to extra-firm HT-840 for high-closure-force enclosure gaskets. Silicone sponge offers low compression set for outdoor gasketing, while solid silicone rubber provides higher tensile strength, toughness, and long-term resistance to harsh outdoor elements like wind, rain, and humidity; however, silicone sponge and foam typically compress more easily under lower forces than solid stock.
Rubber for Outdoor Exposure
Solid EPDM resists heat, ozone, UV, water, steam, alkalis, acids, and oxygenated solvents. However, it is not suited for petroleum oils or fuels such as gasoline, diesel, and kerosene.
Neoprene (CR): General-Purpose Weather and Flame Resistance.
Solid neoprene offers good resistance to weather, ozone, and UV, plus inherent flame resistance. Its resistance to oil and gas is moderate, so verify fluid and temperature limits for the specific compound.
3M™ Extreme Sealing Tape
Extreme sealing tape pairs an acrylic pressure-sensitive adhesive with a flexible TPO backing that conforms to screw heads, rivets, joints, and splices. It protects gaps, seams, joints, and other penetrations from water intrusion, sealing immediately without the cure time liquid sealants require.
Epichlorohydrin (ECH): Heat, Oil, and Fuel Resistance
Monarch ECH foam is rated for temperatures from -40°F to 300°F, resists ozone, oil, and fuel, and seals components in high-heat applications. Grades range from soft Monarch 4051 to firmer Monarch 4053, with soft-to-medium Monarch 4052 in between. Resistance varies by fluid and temperature, so verify the limits for the specific grade.
3M™ VHB™ Tape: An Alternative to Rivets and Welds
VHB acrylic foam tapes bond to aluminum, steel, glass, plastics, and painted or powder-coated surfaces, and they resist solvents and moisture. Occasional contact with fluids such as gasoline, motor oil, or hydraulic fluid should not affect performance in most applications, but continuous submersion in chemical solutions is not recommended. Choose the right series for the application to ensure best adhesion. VHB does not adhere equally to all plastics. High-surface-energy plastics (like acrylic or polycarbonate) bond easily, but low-surface-energy (LSE) plastics (like polyethylene and polypropylene) often require a specialized series (such as the 3M VHB LSE series) or a surface primer.
Butyl Tapes and Sikaflex® Sealants: Seals That Move with the Joint
Butyl tapes combine elasticity with high tack, maintaining a watertight seal even when the joint moves. For example, SikaLastomer® butyl tapes waterproof rivet and lap seams in truck trailers and RVs. Sikaflex® polyurethane sealants can form flexible seals in moving joints. Select the specific product for the substrates, expected movement, and fluid exposure, and follow its joint-design, surface-preparation, and curing requirements. Where vapor resistance is critical, verify it separately.
Silicone PSA vs. High-Performance Acrylic PSA
For adhesive-backed parts, the adhesive is included in the rating. Norseal® 100S silicone sponge tape with a silicone PSA is rated to 260°C (500°F); Norseal 200A with an acrylic PSA is rated to 163°C (325°F).
Temperature Comparison
| Material | Temperature Range | Selection Considerations |
|---|---|---|
| BISCO® silicone foams (BF-1000, HT-800, HT-820, HT-840, HT-870) | -55°C to 200°C (-67°F to 392°F) | Soft to extra-firm grades; UL 94 V-0 |
| BISCO 7304 / 7330 silicone sponge | -55°C to 232°C (-67°F to 450°F) | Closed-cell; flame-resistant |
| Norseal® 100S silicone sponge tape | -73°C to 260°C (-100°F to 500°F) | Silicone PSA |
| Norseal 200A silicone sponge tape | -29°C to 163°C (-20°F to 325°F) | Acrylic PSA |
| 3M™ Extreme Sealing Tape | Long-term to 93°C (200°F); short-term to 149°C (300°F) | Minimum application temperature 10°C (50°F) |
| Norseal AST 5010, 5020, 5110 sealing tape | -40°C to 100°C (-40°F to 212°F) | UV-resistant carrier film |
| Butyl tape (mastic): SikaLastomer®-95 / -65 | -51°C to 100°C (-60°F to 212°F) | No cracking at -51°C (-60°F) |
ECH and EPDM: Matching the Material to Heat, Cold, and Fuel
Epichlorohydrin (ECH) rubber combines fuel and oil resistance with ozone resistance and offers greater heat resistance than nitrile, though its temperature limits vary by grade. EPDM covers a wide temperature range, but it is not suited for petroleum oils or petroleum-based fuels.
Fuel, Oil, and Chemical Screening
| Material | Fuel and Oil | Chemicals | Key Considerations |
|---|---|---|---|
| Solid nitrile (NBR) | Superior resistance to petroleum-based hydraulic fluids, oil, and gasoline | Good resistance to dilute alkalis and acids | Limited weather resistance |
| Solid EPDM | Not suited to petroleum oils or petroleum-based fuels | Alkalis, dilute acids, oxygenated solvents; water and steam | Resists heat, ozone, and UV |
| Silicone (solid and sponge) | Confirm by grade | Many chemicals | Confirm against the specific chemical |
| Vinyl nitrile (PVC/NBR) foam | Highly oil resistant | Confirm by grade | Closed-cell; UL 50E listed for gasketing |
| PTFE film tape | Confirm adhesive compatibility | Chemically inert backing | Silicone adhesive is attacked by organic solvents |
| ECH foam (Monarch 4051, 4052, 4053) | Superior oil and fuel resistance | Confirm by grade | Closed-cell; resists heat and ozone; rated -40°F to 300°F |
Low Temperatures: Service Range vs. Brittleness Point
Minimum service temperatures for solid rubber vary by polymer: -80°F for silicone, -40°F for EPDM, -20°F to -40°F for nitrile, and -20°F for neoprene. The brittleness point is a separate measure. ASTM D2137 determines the lowest temperature at which a rubber will not fracture under a specified impact.
Materials expand and contract with temperature, so a seal must remain flexible enough to accommodate this movement. SikaLastomer-95 and -65 butyl tapes show no cracking or loss of adhesion at -51°C (-60°F).
Adhesive-Backed Products: Apply Warm, Seal Cold
Minimum application temperature can exceed minimum service temperature. Most VHB™ tapes should be applied at 10°C (50°F) or higher, though once properly applied, the bond generally holds at temperatures below the application minimum.
Matching Seals to Fuels, Oils, and Chemicals
Compatibility depends on the specific fluid, concentration, temperature, exposure time, and formulation. Fuels and oils require different materials than acids, alkalis, and solvents, so evaluate each exposure separately.
Fuel and Oil Exposure: ECH, NBR, and Vinyl Nitrile
Solid nitrile (NBR) offers superior resistance to petroleum-based hydraulic fluids, oil, and gasoline. ECH also resists fuels and hydrocarbon oils and provides better heat and ozone resistance than nitrile. Among closed-cell foams, vinyl nitrile is highly oil-resistant, and neoprene foam offers good oil resistance.
Chemical Exposure: Acids, Alkalis, and Solvents
EPDM resists alkalis, dilute acids, and oxygenated solvents, and nitrile offers good resistance to dilute acids and alkalis. Neither is suited to concentrated nitric acid, and concentration and temperature affect every rating. Silicone resists many chemicals, but compatibility should be confirmed for each specific chemical. SikaLastomer® butyl tapes resist water and alcohols but have poor resistance to organic solvents.
Hidden Failure Points
Fluids can swell, shrink, soften, or harden rubber, changing gasket fit and its ability to maintain sealing contact. Evaluate dimensional and mechanical-property changes after representative fluid exposure, then confirm that the exposed gasket still seals in the assembly.
The adhesive can fail first. A chemically inert PTFE backing doesn’t protect its silicone adhesive from organic solvents.
Closed-cell doesn’t mean immersion-ready. VHB™ LSE tape uses 100% closed-cell foam, but continuous submersion in chemical solutions is not recommended.
Substrate, tape thickness, surface preparation, and application pressure all affect performance. For rigid, flat substrates, 3M recommends considering VHB tape 1.1 mm (45 mil) or thicker.
Match the test to the construction. ASTM D471 is intended for solid rubber, while ASTM D1056 specifies fluid-immersion tests for sponge and expanded rubber.
Foam, Sponge, or Solid Rubber: Which Construction Fits?
The same polymer can be supplied as open-cell foam, closed-cell foam, or solid rubber. Open-cell foam allows vapor and liquids to pass through, and often air, depending on the product. Closed-cell foam, by contrast, resists water, vapor, and air, making it a natural sealing material.
Closed-Cell Foam and Sponge: Gap Filling and Environmental Gasketing
Closed-cell foams fill gaps, compress, and seal against liquid penetration. Select gasket thickness and firmness against the minimum and maximum assembled gaps: the gasket must maintain sealing contact at the largest gap without excessive compression or closure force at the smallest.
Silicone sponge (BISCO® 7130, 7304, 7330): offers a wide temperature range and conforms to irregular surfaces and maintains a low compression set.
Closed-cell EPDM foam: suitable for weather and ozone exposure.
Vinyl nitrile (PVC/NBR) foam: is highly resistant to oil and flame and seals against moisture and gas.
ECH foam (Monarch 4051, 4052, 4053): resists high temperatures, oil, and fuel, and limits water absorption to 5%, making it suitable for sealing in heat- and fluid-exposed assemblies.
Neoprene and blended neoprene foam: general-purpose options for weather exposure and selected oils and chemicals. Where UL requirements apply, select a grade with documented recognition for the intended use and verify its conditions of acceptability.
When durability matters more than compressibility, solid rubber absorbs shock, impact, and abrasion and can serve as a liquid seal in solid-section gaskets. Typical uses include ship bearing pads, vibration mounts, and loading dock bumpers.
Frequently Asked Questions
Can 3M™ Extreme Sealing Tape be used for continuous chemical or fluid immersion?
3M™ Extreme Sealing Tape protects against water intrusion, not continuous immersion or aggressive process chemicals, so confirm suitability before use.
Why can seals leak in extreme cold?
Elastomers contract more than rigid substrates during temperature drops, creating physical gaps. Extreme cold stiffens materials and reduces elasticity, preventing the seal from recovering and maintaining the constant surface pressure required to block fluids. When specifying materials for low-temperature environments, engineers must verify the minimum service temperature, low-temperature brittleness limits (such as ASTM D2137), and, for adhesive-backed components, the minimum application temperature.
Does the adhesive need to resist the fluid as well?
Yes. A chemically inert backing won’t protect an adhesive that the fluid attacks, so the entire construction, including the adhesive, must withstand the exposure.
Choose Sealing Materials for Your Application
Chemical compatibility, fluid exposure, temperature, environment, material form, and adhesive all inform the right material choice. Engineered Materials supplies and converts materials to match each application.
Let’s discuss what’s possible. Contact Engineered Materials to discuss your application.