UV Resistant EPDM Grommets for Solar mounting system
The Engineering Problem
Solar mounting systems place elastomeric components in one of the most demanding outdoor exposure profiles in common industrial use: continuous UV radiation, daily thermal cycling between ambient and panel-heat temperatures, and atmospheric ozone — sustained over a service life that is typically expected to reach 25 years or more. Standard commercial rubber compounds are not formulated for this combination of stressors. Continuous UV and ozone exposure causes progressive surface cracking in susceptible elastomers, which destroys the mechanical integrity of the seal at racking and panel interfaces. Once cracking penetrates the compression zone, water ingress follows — compromising internal connection points, triggering IP rating failures in electrical enclosures, and creating field replacement cycles that erode the economics of the installation.
Selecting the right elastomer for this environment is not simply a matter of choosing a “weather resistant” material. It requires a compound whose base polymer chemistry is inherently resistant to the specific attack mechanisms present, and whose cure system and geometry are matched to the thermal cycling loads the application imposes.
Why Peroxide-Cured EPDM Works for This Application
EPDM’s UV and ozone resistance is rooted in its polymer backbone. Unlike diene rubbers — which contain reactive double bonds in their main chain that ozone and UV radiation attack directly — EPDM has a fully saturated backbone. There are no vulnerable double bonds along the primary chain for ozone to cleave, which is why EPDM is the standard material of choice for long-duration outdoor exposure in demanding applications such as automotive weatherstripping, roofing membranes, and increasingly, solar infrastructure.
Within EPDM grades, the cure system matters for a different but equally important reason: long-term sealing performance under thermal cycling. A grommet in a solar mount is compressed at installation and then subjected to daily temperature swings that load and relax the elastomer continuously. The relevant failure mode here is compression set — the permanent deformation that causes a seal to lose contact force over time. Peroxide-cured EPDM produces carbon-carbon crosslinks, which have higher thermal stability than the sulfidic bonds formed in sulfur curing. This translates to lower compression set under sustained and cyclic heat loading, meaning the grommet maintains its contact force against the mounting rail over years of operation rather than flattening out. Sulfur-cured EPDM offers higher initial tensile and tear strength, but for a static compression seal in a thermally cycled environment, the peroxide-cured compound’s aging stability is the property that governs long-term performance.
How We Approach Custom Fabrication
Fenlora Groups does not manufacture standard catalog parts. If your application involves extended outdoor UV exposure, sustained panel compression, or specific sheet metal interface requirements, we develop the compound specification and part geometry around those conditions.
For grommet profiles, retention lip geometry and panel thickness tolerance are specified to the mounting rail to ensure consistent compression at installation — because a grommet that is undersized or oversized for the panel slot will not maintain sealing force regardless of how good the material is. We process both molded grommet profiles and UV-resistant EPDM sheet material, which allows us to address flat gasketing requirements alongside molded components using a matched compound specification. Tooling is cut to the actual shrinkage rate of the specific EPDM compound, not a generic estimate, which matters for parts that need to seat flush in tight-tolerance rail channels.
Technical Specifications
| Property | Typical Value | Test Standard |
|---|---|---|
| Ozone Resistance | No Cracks (100 pphm, 20% strain, 40°C, 70 hrs) | ASTM D1171 |
| Weathering Resistance | Excellent retention of physical properties | Per ASTM D750 exposure protocol |
| Durometer (Hardness) | 60 +/- 5 Shore A | ASTM D2240 |
| Tensile Strength | 1450 psi (10 MPa) minimum | ASTM D412 |
| Compression Set | 25% max (22 hrs at 100°C) | ASTM D395 Method B |
| Recommended Application Conditions | -40°C to +125°C, direct sunlight exposure | Operating Metric |
Material Comparison
Peroxide-Cured vs. Sulfur-Cured EPDM: Both cure systems share the same UV and ozone resistance, which comes from EPDM’s saturated polymer backbone rather than the crosslink chemistry. The distinction that matters for solar mounting applications is long-term compression set under thermal cycling. Peroxide curing produces carbon-carbon crosslinks with higher thermal stability, which results in better retention of compression force over years of heat loading. Sulfur curing offers advantages in initial tensile and tear strength and is often lower cost, but for a static compression seal exposed to sustained cycling, the peroxide-cured compound’s aging behavior is the governing factor.
Peroxide-Cured EPDM vs. Neoprene: Engineers sometimes research neoprene for outdoor mounting applications given its general weather resistance. The distinction is in backbone chemistry. Neoprene’s polymer chain retains residual double bonds that remain susceptible to ozone attack over long service durations, producing progressive surface cracking. EPDM’s fully saturated backbone eliminates this mechanism, making it the technically superior choice for applications where ozone resistance across a 20- to 25-year service life is a design requirement.
Request a Quote and Prototype Tooling
Fenlora Groups handles custom production runs with flexible MOQs starting as low as 100 pieces, depending on part size and complexity. We offer rapid prototype tooling to validate fit and function before committing to production molds. Contact us today to request a quote.