If you design or maintain outdoor electrical enclosures, you already know how critical the gasket is.
It’s the unsung hero that keeps out water, dust, UV radiation, and temperature extremes — ensuring reliability year after year.

But not all gaskets are created equal. Choosing the wrong rubber material or profile can lead to leaks, premature cracking, or loss of compression set, putting your entire system at risk.

That’s where EPDM and custom manufacturing come in.

Why EPDM Is the Go-To for Outdoor Gaskets

EPDM (Ethylene Propylene Diene Monomer) is one of the most weather-resistant rubber compounds available. It’s engineered to handle UV exposure, ozone, moisture, and temperature swings without breaking down — which is exactly what outdoor enclosures face daily.

Key advantages of EPDM rubber include:

  • Excellent UV and ozone resistance (unlike natural rubber, which cracks outdoors)
  • Wide temperature range: typically -40°C to +120°C
  • Outstanding water sealing and electrical insulation
  • Good compression set resistance, maintaining seal integrity over time
  • Resistant to mild chemicals and acids

Because of these traits, EPDM is used across solar power, telecom, HVAC, marine, and electrical distribution industries — anywhere a reliable outdoor seal is required.

The Importance of Compression Set Resistance

In long-term gasket performance, the most common failure mode isn’t cracking — it’s compression set.
That’s when the rubber permanently flattens out after being compressed for months or years, reducing its ability to maintain a seal.

EPDM’s molecular structure gives it excellent resilience, allowing it to spring back after repeated compression.
When combined with the right durometer (typically 50–70 Shore A for enclosure gaskets), it maintains sealing pressure even after long-term use.

Gasket Design Considerations

When designing a gasket for outdoor enclosures, pay attention to the following:

1. Cross-Section and Profile

Common shapes include D-shape, P-shape, and bulb seals.
For custom enclosures, a molded continuous gasket (rather than extruded and joined) often provides the most reliable, leak-free seal.

2. Mounting Method

Decide how the gasket will attach:

  • Adhesive-backed for easy installation
  • Push-in styles for groove-mounted seals
  • Bonded-in-place gaskets for precision or permanent applications

3. Durometer and Fit

A softer rubber improves sealing on uneven surfaces, while harder rubbers handle higher compression forces.
Testing with prototypes ensures the right balance of compression and rebound.

4. Environmental Exposure

Consider long-term exposure to:

  • Direct sunlight and ozone
  • Standing water or humidity
  • Industrial pollutants or salt spray

EPDM performs best here, but specialized coatings or blends can add even more protection when needed.

Custom Molding vs. Extrusion

Many enclosure gaskets are extruded, but if your design involves:

  • Corners that must be sealed perfectly
  • Irregular cross-sections
  • Unique mounting features

Then custom rubber injection molding is the better choice.
Molded gaskets eliminate seams, improve dimensional accuracy, and provide consistent performance across production runs.

At Primo Rubber Co., we specialize in custom molded EPDM components that fit precisely and perform under harsh conditions.

Why Work with a U.S.-Based Manufacturer

Sourcing gaskets overseas can be tempting, but when it comes to critical sealing parts, quality and turnaround time matter more than pennies per part.

With Primo Rubber Co., you get:

  • Domestic production and faster lead times
  • Access to experienced engineers who understand your application
  • Consistent quality and traceability
  • Material testing and formulation options for your exact environment

We don’t just ship parts — we partner with you to ensure your enclosures stay sealed and reliable for years.

Seal It Right the First Time

A gasket might seem like a small detail, but in outdoor electrical systems, it’s the line between reliability and failure.

At Primo Rubber Co., we design and mold custom EPDM gaskets that hold up to the elements.
Whether you need a new design or a drop-in replacement for an existing seal, our U.S.-based team can help you build a better, longer-lasting part.

Contact us today to discuss your custom EPDM gasket project — and seal your enclosures with confidence.