Room-temperature-cure silicone covers everything from a deep electronics potting compound to a near-gel cushion built to absorb shock rather than resist it — the shared “cures without an oven” trait says nothing about which mechanical job a given grade is actually built for. Incure’s Pyra-Sil™ RTV silicone line spans that range across five grades, and matching one to a job means starting with function, not just working time or viscosity.
621 Is Built for Deep-Section Electronics Potting
Pyra-Sil™ 621 is a two-part (100:5 mix ratio) room-temperature-cure silicone formulated specifically for deep-section potting and encapsulation, protecting electronic components against thermal stress, vibration, and moisture ingress. Its 45-minute working time is the longest in the line by a wide margin, giving an operator real time to fill a deep cavity before the material starts to set — a genuine requirement on deep pours where a shorter pot life would risk the material skinning over before the cavity is fully filled. It’s also the hardest grade in the line at Shore A45–A55 and carries the highest tensile strength at 375 PSI, reflecting that 621 is chosen where the potted assembly needs real mechanical protection, not just a soft cushioning fill. Applied by manual mixing or static-mix dispensing, it holds the same broad -45°C to 260°C service range shared across most of the line, so the deciding factor between 621 and the general-purpose grades below it is almost always working time and mechanical protection rather than temperature tolerance.
873 and 892 Both Handle General Sealing and Gap-Filling, Split by Cure Speed
Pyra-Sil™ 873 is a moldable, self-leveling silicone gel for sealing, potting, seam-filling, and encapsulation on metals, plastics, and glass, curing fully in 180 minutes at room temperature or accelerated to 15 minutes at 150°C where oven capacity is available. Pyra-Sil™ 892 covers similar ground — deep sealing, seam-filling, encapsulation, form-in-place gaskets, and potting — but with a genuinely faster process: just a 3-minute working time and a full cure in 15 minutes to an hour, the fastest room-temperature cure path in the entire line. The two also differ in viscosity structure: 873 is a thin, self-leveling 800–1,200 cP single-stream material, while 892 is dispensed as two separately metered components — Part A at 18,000–26,000 cP and Part B at 6,000–10,000 cP — through a static mix system, a setup suited to production lines already running static-mix dispensing equipment rather than manual pour-and-level application. Both bond to metals and plastics, and 873 additionally bonds to glass, worth checking directly if a job spans all three substrate types on the same assembly rather than assuming either grade covers glass by default.
Email Us with your substrate, working-time requirement, and whether the joint needs to seal, pot, bond, or absorb shock, and Incure’s engineers can confirm which Pyra-Sil™ RTV grade actually fits.
874 Is the Specialist for Plastics Most Adhesives Can’t Bond
Pyra-Sil™ 874 solves a different problem entirely: bonding and sealing plastics that are notoriously difficult to adhere to, including polyethylene, polypropylene, and thermoplastic elastomers. It’s the only one-part grade in the line, formulated as a thixotropic paste with an 8-minute pot life and a 20-minute tack-free cure, positioned as a bonder, sealant, and form-in-place gasket material in one. At 350,000–450,000 cP, it’s also by far the thickest grade in the line — a paste consistency that holds its shape on a gasket bead rather than self-leveling, which matters specifically because the low-surface-energy plastics it’s built for often need the adhesive to stay put on a vertical or contoured joint rather than flow away before cure.
875 Trades Strength for Shock Absorption
Pyra-Sil™ 875 is a two-part, fast-curing silicone rubber built specifically for shock dampening and vibration isolation rather than structural bonding. At Shore A0–A5 — by a wide margin the softest grade in the line, closer to a gel than a conventional elastomer — it’s formulated to cushion severe impact rather than resist it the way 621’s harder, higher-tensile chemistry does. Its 15-minute pot life sits between 892’s fast 3-minute working time and 621’s long 45-minute window, a middle ground suited to moderate-complexity cushioning applications that don’t need 621’s extended deep-pour working time.
Where the Line Fits
Electronic assembly potting favors 621 wherever the potted component needs real mechanical and thermal protection over an extended fill time, while 892 and 873 cover general-purpose sealing, gasketing, and encapsulation work split by whether the line already runs static-mix dispensing equipment. Bonding low-surface-energy plastics — PE, PP, and TPE components that reject most conventional adhesives — is 874’s specific niche. Shock-sensitive assemblies, from vibration-prone electronics to impact-exposed enclosures, rely on 875’s near-gel softness rather than any of the structural grades above it. Facilities already running Incure’s peelable silicone adhesive line for temporary masking or removable conformal coating can add this RTV line specifically where the silicone needs to stay bonded permanently rather than peel away by design.
Contact Our Team to confirm the Pyra-Sil™ RTV grade for your substrate and mechanical requirement.
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