Epoxy / Putty

High-Temperature Epoxy: A Solution for Extreme Environments

Standard epoxy is prized for strength and adhesion, but most grades start to soften somewhere between 60 and 90°C. High-temperature epoxy is engineered to hold its mechanical properties well above that, making it the material of choice where heat would defeat an ordinary bond. What Sets High-Temperature Epoxy Apart The key metric is glass transition temperature (Tg), the point at which the cured polymer shifts from a rigid glass to a soft, rubbery state. Above Tg, shear and tensile strength drop steeply. High-temperature epoxies use aromatic hardeners, specialized curing agents, and often mineral or ceramic fillers to push Tg into the 150 to 250°C range, with some formulations rated for short-term exposure much higher. Alongside raised Tg, these grades typically offer: Retained strength at temperature, not just survival of a heat spike. Low coefficient of thermal expansion, often through ceramic or silica filler, which limits dimensional drift. Oxidative and chemical stability so the polymer does not embrittle during long hot service. Where It Is Used Automotive and motorsport: bonding and sealing near exhaust manifolds, turbochargers, and engine covers where under-hood temperatures routinely exceed 120°C. Aerospace: structural bonding of composite and metal assemblies, plus sealing around bleed-air and engine nacelle components. Electronics: die attach, encapsulation, and coil bonding where resistive heating and power density raise local temperatures. For high-power resistor and heater coatings, ceramic-filled dielectric grades are common. Energy: downhole tools, geothermal equipment, and solar concentrator assemblies exposed to sustained heat. Industrial process equipment: bonding and patching on ovens, dryers, kilns, and steam systems. For external surfaces that must radiate heat or survive flame contact, high-emissive ceramic coatings selected by substrate and service temperature often pair with a high-temperature epoxy bond underneath. Cure and Post-Cure High-temperature epoxies almost always require a heat cure and a post-cure to reach full Tg. A representative schedule ramps to an initial cure temperature, holds, then steps up to the post-cure temperature for one to several hours before a slow cool-down. Curing at room temperature alone can leave the polymer 40 to 60°C short of its rated Tg and dramatically weaker when hot. Control the ramp rate. Fast heating traps reaction exotherm in thick sections, which can char the resin or generate porosity from escaping volatiles. Not sure which grade and cure schedule your assembly needs? Email Us with your continuous and peak temperatures and substrate list. Designing the Joint Heat magnifies the effect of expansion mismatch. When a high-temperature epoxy bonds steel to aluminum, or metal to ceramic, each thermal cycle shears the bond line because the two substrates grow at different rates. A filled, lower-CTE epoxy reduces the internal stress, and joint geometry does the rest. The underlying mechanism is laid out in this explainer on how CTE mismatch causes adhesive bond failure. Practical guidance: Keep bond lines thin and uniform, 0.1 to 0.3 mm, to limit stress and voids. Favor shear-loaded lap joints over peel or cleavage. Radius sharp corners where stress concentrates. Verifying Performance Rate the epoxy on wet Tg, since absorbed…

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November 27, 2024
Putty

Incure Epo-Weld™ High-Temperature Sealing Epoxy for Gaskets and Equipment

Equipment that runs between 300°C and 500°C sits in an awkward gap: too hot for elastomer gaskets, not hot enough to justify a rigid furnace-grade cement that would crack under vibration. A fiber-filled ceramic gel fills that range with a seal that stays slightly pliable. The mid-temperature sealing gap Nitrile, silicone, and fluoroelastomer gaskets top out well below 300°C. Above that, they harden, take a permanent set, and lose the recovery force that keeps a bolted joint tight. Move up to a hard, fully rigid ceramic and a new problem appears: with no give at all, the seal cracks wherever the flanges flex, breathe with pressure, or vibrate. Incure's Epo-Weld™ high-temperature sealing compound is engineered for the middle ground. It is a one-part ceramic gel reinforced with fibers, rated for continuous service to roughly 510°C (950°F). The fiber network keeps the cured seal tough and marginally flexible so it tolerates the small, repeated movements that a mid-temperature flange sees, while the ceramic matrix carries the heat and resists the chemicals that would attack an organic gasket. What the compound is The material is supplied as a thick, non-slumping gel that stays in place on vertical and overhead sealing faces. Being single-component, it needs no mixing and has no pot life once opened. It wets and lightly bonds to steel, stainless, and cast iron, and after cure it resists steam, combustion gases, oils, and dilute acids and alkalis. Typical uses Gasketing boiler doors, economizer access panels, and soot-blower ports Sealing ducting, dampers, and expansion joints on flue-gas systems Flange seals on blowers, compressors, and steam valves Oven and dryer panel joints, and heat exchanger header covers Sealing pump and gearbox covers on hot process service How to apply it Strip both faces to bare metal, removing every trace of old gasket, oil, and oxide. Run a continuous bead inside the bolt circle, sized so it stands slightly proud of the target joint gap. Assemble the joint while the gel is wet and torque the fasteners in a star pattern to the equipment specification, letting the material squeeze out to a thin, even witness line. Remove the squeeze-out before it skins over. Give the joint 24 hours to air-dry, then bring it up to temperature gradually on first firing, pausing near 100°C and near 250°C so entrained moisture leaves as vapor rather than as steam pressure inside the bead. This staged first heat is where the seal gains its final strength. For choosing a sealing or bonding material by how far the mating parts move, see how CTE mismatch causes adhesive bond failure, and for higher-temperature service compare Incure's ceramic coatings organized by substrate and service temperature. Why fiber reinforcement matters An unfilled ceramic binder is hard and brittle; it seals well until the first thermal shock or vibration event opens a crack. Chopped fiber distributed through the gel bridges microcracks as they form and blunts their growth, so the seal keeps its integrity through many more heat cycles. The trade-off is…

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August 10, 2024
Putty

Incure Epo-Weld™ High-Temperature Epoxy Gasket Seal for Extreme Heat

When a boiler door, a furnace access panel, or a molten-metal launder needs a gasket, rubber and cork are out of the question. Sealing surfaces that run above 1,000°C calls for a formed-in-place ceramic gel that stays sealed through every heat-up and cooldown cycle. The problem with conventional gaskets at high temperature Elastomeric and fiber gaskets rely on compression set: they are squeezed between two flanges and their recovery force keeps the joint tight. That mechanism collapses at high temperature. Organic binders in sheet gaskets burn out, leaving a loose ash; ceramic fiber ropes relax and shrink; and every heat cycle widens the gap as the flanges distort. The result is a joint that leaks combustion gas, radiant heat, or process fumes within a handful of cycles. Incure's Epo-Weld™ high-temperature gasket compound is a one-part ceramic gel filled with reinforcing fibers. It is applied wet directly to the sealing face, then the joint is closed so the material takes the exact shape of both surfaces. On cure it forms a dense, slightly resilient ceramic seal rated for continuous service to roughly 1,300°C (2,400°F). Because it is formed in place, it fills machining marks, minor warpage, and pitting that a cut gasket would bridge over and leak past. What the compound is The gel is thick enough to stay where it is placed on a vertical face and does not slump before the joint is assembled. It is single-component, so there is no mixing, and it bonds lightly to steel and cast iron so it stays put during assembly. Once cured it resists most process chemicals, combustion products, and mild acids and alkalis, which makes it suitable for equipment where the seal sees both heat and corrosive exposure. Where it fits Boiler and furnace doors, peep sights, and access hatches Ductwork and expansion-joint flanges on hot-gas systems Molten-metal handling equipment, launders, and ladle covers Blowers, compressors, and steam valve bonnets on high-temperature service Manifolds, heat exchangers, and oven panel joints For selecting protective materials by peak temperature and base metal, Incure's guide to ceramic coatings by substrate and service temperature is a useful companion. Application Clean both flange faces to bare metal and remove all old gasket residue, oil, and scale. Lay a continuous bead of gel inside the bolt circle, slightly proud of the final joint thickness, and close the joint immediately while the material is still wet. Torque the fasteners in a cross pattern to the equipment manufacturer's specification so the gel is compressed evenly and squeezes out to a thin, uniform line. Wipe the excess before it skins. Allow the assembly to air-dry for 24 hours. The seal then develops full ceramic strength through the first heat-up. Where possible, bring the equipment to operating temperature in stages rather than a single fast ramp, holding near 100°C and again near 250°C to let residual water escape as vapor without pressurizing the joint. A joint that is heated too quickly can bubble or crack along the bead. Thermal cycling and…

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August 10, 2024