On a high-mix electronics line, the slowest step is often waiting for a sealant to set before the assembly can move. A silicone that fixtures in roughly ten seconds under UV light, then finishes curing on its own in hidden areas, removes that bottleneck. Incure Pyra-Sil™ 915 is a one-part, UV/moisture dual-cure silicone designed for form-in-place gaskets, conformal coating, and general sealing.

Two Cure Mechanisms, One Material

The primary mechanism is UV or UV-LED photopolymerization. Exposed resin gels in about ten seconds, giving immediate handling strength and a tack-free surface. The secondary mechanism is a room-temperature moisture cure that completes crosslinking in shadowed regions, typically over about 72 hours depending on section thickness and ambient humidity.

That combination matters because pure UV silicones leave liquid resin wherever light cannot reach: under a bead’s overhang, beneath a mating flange, or in the shadow of a tall component. Uncured silicone can migrate, contaminate contacts, or outgas into an enclosure. The moisture-cure backstop converts those pockets to fully crosslinked elastomer without a secondary bake.

Form-in-Place Gasket Use

As an FIPG material, Pyra-Sil™ 915 is dispensed as a bead directly onto one half of an enclosure, UV-fixed so the bead holds its profile and the housing can be handled or inverted immediately, then assembled. The moisture cure finishes the compressed cross-section over the following days.

Key process controls for FIPG work:

• Bead cross-section: Keep the dispensed bead consistent. Under-filled sections lose sealing force after compression set; over-filled beads squeeze out and can bridge to nearby features.
• Compression: Design the groove and land so the cured gasket is compressed 15–30 percent. Too little compression leaks; too much accelerates long-term set.
• UV dose: Verify surface dose with a radiometer. An under-cured skin stays soft and distorts during assembly.

Conformal Coating and Sealing

The same material brushes or sprays as a conformal coating on populated boards, protecting against condensing humidity, dust, and corrosion, and suppressing arcing across high-voltage traces at altitude. Because the cured film is a low-modulus elastomer, it flexes with the board through thermal cycling rather than cracking at solder joints. The stress mechanism that makes rigid coatings risky on mixed-material boards is covered in how CTE mismatch causes adhesive bond failure.

Where 915 Is Used

• Consumer and industrial electronics: Enclosure sealing and board protection where cycle time drives cost.
• Automotive modules: Sealing control units and sensor housings against underhood heat and moisture.
• Renewable energy hardware: Gasketing inverter and combiner enclosures exposed to outdoor weathering and ozone.
• Lighting and signage: Sealing outdoor luminaire housings and driver compartments.

Durability and Environmental Resistance

Cured Pyra-Sil™ 915 resists ozone, UV weathering, and elevated temperature, and stays dielectrically stable when damp. Silicone’s weak point is mechanical: it is not abrasion-resistant and offers modest tensile and tear strength compared with a rigid structural adhesive. Use it where sealing, dielectric protection, and stress relief matter, and use a structural adhesive where load transfer matters. The trade-offs between fast light-cure chemistries and higher-strength systems are laid out in UV glue versus epoxy for heavy-duty repairs.

Common Mistakes

The most frequent error is sealing finished assemblies in a dry barrier bag before the moisture cure completes. Without ambient humidity, shadowed silicone stays liquid indefinitely. The second is relying on lamp timers instead of measured dose; LED output drifts down over thousands of hours, and a slow decline shows up as tacky coatings long before anyone suspects the lamp. Selecting cure equipment against a documented output spec, as in Incure’s L-Series flood lamp guide, prevents that drift from reaching product.

A third mistake is skipping surface prep. Silicone needs a clean, dry substrate; flux residue and mold-release films are the usual cause of adhesion loss under an otherwise intact bead.

Depth of Cure and Section Thickness

The UV mechanism only cures what light reaches. In a thick FIPG bead or a filled cavity, the light-cured skin can be firm within seconds while the interior stays fluid, relying entirely on the moisture mechanism to finish. Moisture cure advances from the exposed surface inward at a rate measured in millimeters per day, so a 6 mm section can take several days to fully crosslink at its core. Plan the assembly sequence around that: do not load a bonded joint mechanically, and do not subject it to pressure or solvent exposure, until the section has had time to cure through.

If the design needs a deep section cured quickly, either reduce the bead cross-section, add a light path so more of the volume sees UV directly, or accept a staged process where the part is fixtured immediately and released to full service after a documented cure dwell. Verifying core cure on a sacrificial sample, by sectioning a cured bead and checking for soft material, is worth doing once during process qualification.

Specifying 915

Choose Pyra-Sil™ 915 when you need fast UV fixturing, reliable cure in hidden geometry, elastomeric sealing, and outdoor durability, and when your process can provide the humidity and dwell time the secondary cure needs. For a dispensing recommendation or a trial on your enclosure geometry, Email Us with your groove design, bead length, and cycle-time target.

Incure’s engineers can help you set bead size, compression, and UV dose, and qualify the sealing process against your validation plan. Contact Our Team to begin an evaluation.

Visit www.incurelab.com for more information.