Epoxy Archives - Page 23 of 23

What is the Difference Between Adhesive Failure and Cohesive Failure?

When a bonded joint comes apart, the way it separated tells you why. Adhesive failure and cohesive failure look similar at a glance but point to completely different root causes, and reading the fracture surface correctly is the fastest route to a fix. What Adhesive Failure Looks Like Adhesive failure occurs at the interface between the adhesive and the substrate. The adhesive releases cleanly from one surface, leaving that face bare while the full adhesive layer stays on the opposite part. It means the bond to at least one substrate never developed properly. Common causes: Surface contamination. Oils, mold release, fingerprints, or oxide layers block molecular contact. Even a monolayer of silicone can drop peel strength by more than half. Inadequate surface preparation. Smooth, low-energy plastics such as polypropylene need abrasion, plasma, or a primer before an adhesive can wet them. Wrong adhesive for the substrate. A chemistry that bonds glass well may have no affinity for a fluoropolymer or a powder-coated panel. Poor wetting. An adhesive that is too viscous, applied too cold, or cured before it could flow will not make full contact with the surface texture. What Cohesive Failure Looks Like Cohesive failure happens inside the adhesive layer itself. Both substrate faces are left coated with adhesive residue, and the split runs through the middle of the bond line. The adhesive gripped both parts successfully, but the material could not carry the load applied to it. Common causes: Incomplete cure. A UV adhesive that received too low a dose stays soft in the core and tears under stress. Dose is intensity multiplied by exposure time, and every adhesive has a published minimum. Aging and environmental attack. Heat, humidity, and light slowly break polymer chains. Hydrolysis and oxidation both reduce cohesive strength over months or years. Overload. The joint was simply asked to carry more force, or more concentrated stress, than the cured adhesive is rated for. Voids and bubbles. Entrapped air concentrates stress and gives a crack an easy path through the layer. Reading the Fracture Surface Set the two separated parts side by side under good light: One clean face, one fully coated face: adhesive failure. Investigate cleaning and surface preparation first. Both faces coated with a torn, fibrous residue: cohesive failure. Check cure completeness and whether the joint is overloaded. A mix across the bond area: a partial or transitional failure, often meaning marginal surface prep combined with marginal cure. Treat both. The substrate itself broke: substrate failure, which usually means the adhesive and the bond were stronger than the part. This is often an acceptable result. Fixing Adhesive Failure Start with the surface. Solvent-wipe with a clean, lint-free cloth and a fast-evaporating solvent such as isopropyl alcohol, changing the cloth often so you are removing contamination rather than spreading it. Abrade low-energy plastics and check surface energy with dyne pens if wetting is marginal. Confirm the adhesive is rated for both substrates, and consider a primer or plasma step for difficult materials. Choosing the…

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July 22, 2024

Adhesive Failure: Root Causes and Effective Solutions

When a bonded joint lets go, the adhesive is usually blamed and rarely at fault. Most adhesive failures trace to how the surface was prepared, how the joint was loaded, or how the environment attacked the bond line. Reading the failure surface tells you which one, and that points straight to the fix. Two failure modes, two different problems Adhesive failure: the break runs cleanly along the interface, leaving one substrate bare and the adhesive stuck to the other. This means the adhesive never properly wet or bonded to that surface, almost always a preparation or compatibility problem. Cohesive failure: the break runs through the adhesive itself, leaving material on both substrates. This means the interface was sound and the adhesive was simply overloaded, under-cured, or degraded. Pulling a failed joint apart and looking at the surfaces is the fastest diagnostic you have. The common root causes Poor surface preparation: oil, mold release, oxide, dust, or moisture forms a weak boundary layer the adhesive bonds to instead of the substrate. This is the single most frequent cause of adhesive failure. Wrong adhesive for the substrate: low-energy plastics, oily metals, and plated surfaces need specific chemistries or primers. A general-purpose adhesive on polypropylene will peel off. Bad joint design: loading a bond in peel or cleavage instead of shear can cut the effective strength by ten times. Cure problems: off-ratio mixing, inadequate mixing, low temperature, or an incomplete UV dose all leave the adhesive below full strength. Environmental attack: heat above the glass-transition temperature, water ingress, solvent contact, and repeated thermal cycling all degrade a bond over time. Differential expansion between dissimilar materials is a major driver, explained in how CTE mismatch causes adhesive bond failure. Overload: the joint simply saw more force, vibration, or movement than it was designed for. The solutions Standardize surface prep: a written clean, abrade, clean sequence with a maximum time from prep to bond, applied the same way by every operator Match the adhesive to both substrates and the environment: check compatibility data and use primers or surface treatment on difficult materials. Grade guidance for plastics is in matching a plastic bonder grade to substrate and mechanical demand, and for glass and metal in matching a UV glass and metal bonder grade to viscosity and tensile requirement Design for shear: maximize overlap area, keep the bond line thin, add edge fillets, and use toughened grades or fasteners where peel is unavoidable Control the cure: metered dispensing for two-part systems, verified light dose for UV, clamping pressure during cure, and a heat post-cure where allowed Qualify against the real environment: soak test coupons at service temperature and humidity, then pull them, before committing to production Email Us with a description of the failure and we will help identify the cause. When adhesive is not enough Some joints carry loads or see conditions that no adhesive alone should be asked to handle. For high-stress structural connections, combine the adhesive with mechanical fasteners so the fasteners carry peak…

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July 22, 2024

Epoxy

Thermally Conductive Epoxy: High-Performance for Demanding Applications

Heat that cannot escape a component shortens its life. Thermal paste moves heat but adds no strength and can pump out over time. Thermally conductive epoxy provides both a heat path and a permanent structural bond, which is why it is used where a joint has to conduct heat and stay put. What Thermally Conductive Epoxy Is Thermally conductive epoxy is a two-part or one-part epoxy loaded with conductive filler, commonly alumina, aluminum, boron nitride, or aluminum nitride. The filler raises bulk thermal conductivity from the roughly 0.2 W/m·K of unfilled epoxy to a range of about 1 to 4 W/m·K depending on grade and loading. The cured material bonds structurally while carrying heat from a source to a sink. Key properties: Thermal conductivity high enough to replace a mechanical clamp plus paste in many designs. Permanent bond between heat source and heat sink, with no pump-out and strong vibration resistance. Gap filling across uneven surfaces, maintaining continuous thermal contact where a rigid clamp would leave air gaps. Electrical behavior by grade. Alumina, boron nitride, and aluminum nitride fillers are electrically insulating; metal fillers are conductive. This distinction has to be chosen deliberately. Advantages Over Thermal Paste and Mechanical Attachment No maintenance. A cured epoxy joint does not dry out, pump out, or need re-torquing. Vibration and shock resistance. The structural bond survives conditions that loosen clips and spring clamps. Part-count reduction. Bonding can eliminate the clamp, spring, and fasteners a paste interface requires. Consistent thermal path. A controlled bond line gives a repeatable thermal resistance across production. Gap tolerance. The epoxy conforms to surface irregularity and warp that defeat a rigid mechanical interface. Choosing the Right Grade Thermal conductivity target. Match the grade to the heat flux. Modest dissipation needs about 1 W/m·K; high-power devices benefit from 2 W/m·K or more. Higher conductivity usually means higher filler loading, which raises viscosity and modulus. Electrical isolation. If the bond line sits between an electrically live surface and a grounded sink, an insulating grade is mandatory. Where the joint is not electrically sensitive, a conductive grade can offer higher conductivity. Confirm the datasheet's volume resistivity, not just a general description. Bond-line thickness. Thinner bond lines have lower thermal resistance but less gap tolerance. Choose viscosity and filler size so the epoxy can be applied at the target thickness without starving the joint. Thermal expansion. The epoxy and the filler expand at different rates from silicon, ceramic substrates, and aluminum sinks. Every power cycle loads the bond. Our explanation of how CTE mismatch causes adhesive bond failure covers why this is the dominant failure mode in thermal-management joints and why a grade with some compliance often lasts longer than a stiff one. Cure schedule. Room-temperature-cure grades simplify the process; heat-cure grades typically develop higher strength and better high-temperature performance. Confirm the assembly can tolerate the cure temperature. Incure's Epo-Weld thermally conductive line covers this range. TC-9051 is a 1:1 grade offering up to about 1.25 W/m·K across a -65 to 205 C…

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June 6, 2024

Epoxy / UV Adhesives

UV Glue vs. Epoxy: Choosing the Right Adhesive for Your Project

UV adhesive and two-part epoxy solve different problems. One trades ultimate strength for speed, clarity, and unlimited working time. The other trades convenience for load capacity, gap filling, and the ability to cure in the dark. Knowing which constraint your joint imposes settles the choice. UV adhesive: fast, clear, light-dependent UV glue is a one-part acrylate or epoxy formulation that stays liquid until light of the right wavelength reaches its photoinitiator, then crosslinks within seconds. Cure speed: fixture strength in 2 to 10 seconds under an adequate lamp, full cure within a minute Working time: unlimited until the light comes on, so alignment is unhurried Clarity: many grades cure water-clear with low shrinkage and controlled refractive index Process temperature: ambient, safe for electronics and optics Constraint: at least one substrate must transmit light, and shadowed areas stay liquid unless the grade has a secondary moisture or heat cure Epoxy: strong, gap-filling, slower Epoxy cures by reacting a resin with a hardener in a fixed ratio, independent of light. Bond strength: lap-shear values commonly 2,000 to 5,000 psi, higher than most UV acrylates Gap filling: tolerates uneven surfaces and bond lines of several millimeters Working time: minutes to hours depending on the system, which allows large or complex assemblies Constraint: requires accurate mixing, cures over minutes to hours, and some systems exotherm enough to matter for heat-sensitive parts Match the adhesive to the dominant requirement Need an instant set on a glass or clear plastic joint: UV adhesive, see which adhesive is better for transparent bonding Need maximum load capacity on an opaque structural joint: epoxy, see which is stronger for heavy-duty repairs Need the shortest possible cycle time: usually UV, see which adhesive dries faster for quick repairs Need to fill a wide or uneven gap: epoxy Need to bond parts you cannot expose to light: epoxy or a dual-cure adhesive Email Us with your joint geometry and load case for a specific recommendation. Cost and process factors beyond the joint UV bonding adds a lamp and, for volume work, a conveyor or chamber, but removes mixing, pot-life waste, and oven time. Epoxy needs little capital equipment but adds metering hardware for repeatable ratios and floor space for cure racks. For high-throughput lines the labor and scrap savings from an instant cure often outweigh the equipment cost; for low-volume or field work, epoxy's simplicity wins. Surface preparation for each UV adhesives depend on a clean, dry, light-transmitting surface. Solvent-wipe glass and plastics with isopropyl alcohol, treat low-energy plastics such as polyethylene or polypropylene with a primer or plasma, and keep the bond line thin so light penetrates fully. Epoxy is more forgiving of minor contamination but rewards abrasion: grit-blasting or sanding to a 60 to 100 microinch profile roughly doubles the effective bond area and moves the failure mode from interfacial to cohesive. Both chemistries fail at a weak boundary layer, so prep discipline matters more than the adhesive grade. Handling and cure defects to watch UV adhesive left partly…

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May 15, 2024

Epoxy

High-Temperature Epoxy for Demanding Bonding and Potting Applications

High-temperature epoxy does two jobs that ordinary epoxy cannot: it holds structural bonds in heat that softens standard resin, and it pots and encapsulates components that run hot without cracking or pulling away. Understanding both roles is the key to choosing the right grade. What High-Temperature Epoxy Is High-temperature epoxy uses heat-resistant resin chemistry and mineral or ceramic fillers to keep mechanical strength and dimensional stability well above the range where general-purpose epoxy fails. Practical continuous service commonly runs to 200 to 250 C, with specific grades rated higher, and short excursions above that depending on formulation. Properties that define the category: Thermal stability. The cured material does not soften near the resin's usual glass transition; strength and stiffness are retained across a wide band. Chemical resistance. Heat-stable backbones also resist fuels, oils, solvents, and process chemicals, in several grades verified through months of immersion. Mechanical strength. Shear and compressive strength stay high enough for structural bonding and load-bearing potting. Low outgassing options. Grades meeting vacuum-service outgassing limits are available for aerospace and instrument use. Formulation range. Fast-set and slow-cure grades, rigid and flexible grades, clear and pigmented grades. Bonding Applications Aerospace: brackets, heat-shield hardware, and engine-adjacent structure. Automotive and transit: exhaust-system components, turbocharger hardware, and sensor mounts near hot zones. Industrial equipment: oven, dryer, and furnace-auxiliary components. Metal finishing repair: rebuilding surface defects in aluminum, cast iron, stainless steel, and steel before powder coating, where the repair must survive the cure oven and the final bake. Potting and Encapsulation Applications Power electronics: potting transformers, inductors, and power modules for thermal management and vibration resistance. Lighting: encapsulating driver electronics and LED assemblies that run at elevated temperature. Sensors and instrumentation: protecting elements that operate in hot process environments. Downhole and process tools: encapsulating electronics under combined heat and pressure. Potting adds a specific stress: the epoxy surrounds the component on all sides, so every heat cycle squeezes and stretches whatever is embedded. A grade that is too rigid can crack solder joints, fracture ceramic parts, or debond from lead wires. Flexible and semi-flexible high-temperature grades exist for this reason. Choosing the Right Grade Confirm the real temperature profile. Identify continuous service temperature and transient peaks. Choose a grade rated above the peak with margin. For potting, also consider the temperature the assembly reaches internally, not just the ambient. Decide rigid versus flexible. Rigid grades maximize strength and abrasion resistance for structural bonds and hard potting. Flexible grades absorb thermal movement and protect fragile embedded components. Our explanation of how CTE mismatch causes bond failure covers why expansion mismatch is the leading cause of potting and bonding failures in thermal cycling. Set the cure schedule. Fast-set grades reach handling strength in minutes but often need a long room-temperature or elevated post-cure to develop full high-temperature properties. Slow grades need a staged bake. Confirm the shop can deliver the required schedule; an incomplete cure softens at service temperature. Check chemical exposure and outgassing. Match immersion and vapor resistance to the environment, and…

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May 7, 2024

Epoxy

Medical Device Epoxies: Adhesives for Reliable Device-Component Bonding

Assembling a disposable diagnostic cartridge or an external fluid-connector set means joining small plastic and metal parts that have to seal, survive sterilization, and pass cytotoxicity testing. The adhesive choice sets how fast the line runs and how well the joint holds. What Sets These Adhesives Apart Adhesives used in device-component assembly are formulated and tested against biocompatibility standards, most commonly ISO 10993-5 for cytotoxicity. Beyond that, they need consistent bond strength on engineering plastics, resistance to the fluids the device contacts, and stability through a validated sterilization cycle. Incure Cyro-Weld grades are formulated to meet ISO 10993-5, and selected grades are validated for ethylene oxide and gamma sterilization; the specific route must be confirmed against each grade's datasheet. These are device-component bonding materials for external and disposable assemblies, not implant adhesives, and no grade here is offered for implanted or long-term tissue-contact use. Chemistry Options UV and visible light-cure acrylates (Cyro-Weld 5000-series): cure in one to several seconds under a spot or flood lamp, cure water-clear, and many grades fluoresce for automated inspection. Grades such as 5002F, 5004F, 5013F, and 5017F cover a viscosity range from wicking to gel. Suited to joints where a light path reaches the bond and cycle time matters. Cyanoacrylate (Cyro-Weld CM-series): single-part instant adhesives that fixture in seconds on elastomers and plastics. Low-viscosity grades such as CM-3 and CM-9 wick into tight joints; higher-viscosity grades such as CM-500 and CM-2500 fill gaps. Good for fast fixture without cure equipment. Two-part epoxy: slower cure but strong, gap-filling bonds across dissimilar materials and shadowed joints a light cannot reach. Used where structural strength and chemical resistance outweigh cycle time. A room-temperature or mild heat cure is chosen based on the temperature limit of the plastics in the assembly. Light-plus-secondary dual-cure grades: a light cure fixtures the part in seconds while a secondary heat or moisture mechanism completes the bond in any shadowed region, useful for opaque housings and blind joints. Email Us with your substrates, joint geometry, and sterilization method, and our team will recommend a grade. Matching Viscosity to the Joint Wicking grades below about 50 cP flow into press-fit and annular gaps by capillary action and cure fast, but drain from open or wide joints. Medium grades hold a bead for positioning. Gel and thixotropic grades fill gaps up to roughly half a millimeter and stay on vertical surfaces. Dispense the minimum volume that completes the joint, since excess adhesive cures slower and can wick where it is not wanted. Substrate Compatibility Common device plastics behave differently. Polycarbonate and ABS bond readily with UV acrylates and CA. Cyclic olefin polymers and polypropylene are lower energy and may need surface treatment or a grade tuned for them. Verify that the cured adhesive resists the specific fluids and cleaning agents the assembly contacts. When the joint pairs a rigid engineering plastic with another part, the Incure Uni-Weld plastic bonder selection guide covers matching a grade to that substrate. Documentation and Change Control Adhesive selection for device-component…

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May 7, 2024

Epoxy

Thermally Conductive Epoxy for Efficient Heat Transfer

A heat sink only works if heat can get into it. Thermally conductive epoxy bonds the component to the sink and carries heat across the joint at the same time, replacing both a fastener and a separate thermal interface material with one cured layer. What Thermally Conductive Epoxy Is Thermally conductive epoxy is a two-part or one-part epoxy loaded with a conductive filler. The epoxy provides structural adhesion and chemical resistance; the filler moves heat. Filler choice sets the two properties that matter most: Alumina and aluminum: moderate thermal conductivity, roughly 0.6 to 1.5 W/mK for alumina-filled grades, at reasonable cost. Aluminum nitride and boron nitride: higher conductivity while staying electrically insulating. Silver: the highest conductivity, but electrically conductive, so it is used only where the joint should also carry current or ground. Real Incure Grades The Incure Epo-Weld thermally conductive epoxy line covers the common cases: TC-9033 and TC-9042: aluminum-filled grades for efficient heat transfer in structural bonding. They are formulated for thermal conduction; they do not carry an electrical-insulation rating, so keep them off exposed conductors. TC-9051: aluminum-nitride-filled, thermally conductive and electrically insulating, for bonding a component directly to a sink where dielectric isolation is required. Email Us with your device, heat sink material, and whether the joint must be electrically isolated, and our team will point to a grade. Why Use It Instead of Grease or a Pad Structural: the cured bond holds the component in place, so no clip, screw, or spring is needed. Thin, stable bond line: cure locks the geometry; there is no pump-out over thermal cycles the way there is with grease. Gap filling: fills uneven or non-flat interfaces that a rigid pad bridges over. Permanent: the trade-off is that a cured epoxy joint is not reworkable, so grease or a pad is the better choice where the component may be replaced. Design Considerations Keep the bond line as thin as the surface flatness allows; a thicker glue line adds thermal resistance no matter how conductive the epoxy is. Control it with spacer beads or a fixture. Because the component, the epoxy, and the sink expand at different rates, thermal cycling shears the bond edge, which is the failure path described in how CTE mismatch causes adhesive bond failure; a slightly more flexible grade or a filleted edge reduces the stress. Follow the specified cure schedule, since an under-cured epoxy has lower conductivity and strength than the datasheet value. Cure Schedule and Its Effect on Properties An epoxy's thermal conductivity, strength, and glass transition temperature are all reported for a fully cured sample. Cut the cure short and every one of those numbers drops. A room-temperature cure reaches usable strength in hours but may take a week to fully crosslink, and the conductivity in the meantime is lower than spec. A heat cure, for example 80 to 150°C for 30 to 120 minutes, completes the network quickly and often yields a higher glass transition temperature and better retention of properties at elevated service…

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May 7, 2024

Epoxy

Ultra High Bond Epoxy for Demanding Structural Applications

When a joint has to carry structural load, resist impact, and survive years of service, the adhesive choice narrows quickly. Ultra high bond epoxy is formulated for exactly those conditions: high tensile and shear strength, toughness under shock, and durable adhesion to a wide range of materials. What Ultra High Bond Epoxy Is Ultra high bond epoxy is a structural adhesive engineered to deliver high load capacity together with resistance to peel and impact, properties that many rigid epoxies sacrifice for stiffness. Toughening chemistry within the resin absorbs energy at a crack tip, so the bond resists sudden loads instead of shattering. Characteristics that matter for structural work: High tensile and shear strength across metals, engineering plastics, composites, ceramics, and masonry. Impact and peel resistance from a toughened, slightly resilient cured matrix. Environmental durability, holding strength through humidity, thermal cycling, and chemical exposure. Wide service range, with grades rated from cryogenic temperatures to elevated-temperature service. Formulation options in viscosity, cure speed, and gap-filling ability. Advantages in Structural Assembly Load spread across the joint. A bonded overlap distributes stress over its full area, avoiding the point loads that start cracks at rivets and bolt holes. Dissimilar-material joining. One adhesive bonds combinations that cannot be welded, such as aluminum to composite or steel to ceramic. Fewer fasteners. Structural bonding can reduce or replace mechanical fasteners, cutting weight and part count. Sealed joints. The bond line also seals against moisture and corrosion at the interface. Fatigue performance. A resilient structural adhesive damps vibration and resists the cyclic loading that loosens fasteners. Applications Manufacturing: bonding high-stress components in machinery, tooling, and equipment frames. Transportation: structural joints in rail vehicles, trailers, and specialty vehicle bodies. Marine: bonding fittings, stiffeners, and panels exposed to salt water and constant flexing. Aerospace: non-primary structural bonding of brackets, fairings, and interior components. Construction and infrastructure: anchoring, structural repair, and bonding of concrete, steel, and stone. Energy: bonding components in wind, solar-tracking, and power-equipment structures. Choosing the Right Grade Define the load case. Quantify the shear, tensile, peel, and impact the joint will see, including worst-case events. Select a grade whose rated strength exceeds the requirement with margin, and prioritize peel and impact ratings where the joint sees shock or vibration. Match materials and manage thermal movement. Bonding two materials with different expansion coefficients means the joint is stressed every time temperature changes. Our explanation of how CTE mismatch causes adhesive bond failure covers why a toughened, slightly flexible grade usually outperforms a rigid one on mixed-material structural joints. Set the working and cure time. Large assemblies need a long open time for fit-up; a fast-setting grade suits small parts and high line rates. Our comparison of which adhesive cures faster for quick repairs covers the trade-off between speed and repositionability. Confirm the environment. Check resistance to the specific chemicals, humidity, and temperature range, and to any immersion service. Account for gap. Choose a grade rated for the actual bond-line thickness; gap-filling grades hold strength in wider or uneven joints.…

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May 7, 2024

Epoxy

Ultra High Temperature Epoxy for Demanding Applications

Standard epoxies lose much of their strength by 120 C and char well before 300 C. Ultra high temperature epoxy is formulated to hold structural bonds where conventional adhesives soften, degrade, or release, making it the practical choice for engine, furnace, and process-equipment bonding. What Ultra High Temperature Epoxy Is Ultra high temperature epoxy uses heat-stable resin chemistry, often combined with ceramic or mineral fillers, to raise the glass transition temperature and slow thermal decomposition. The cured material keeps useful mechanical properties at continuous service temperatures that commonly reach 260 to 300 C, with short-term excursions higher depending on grade. Distinguishing properties: Thermal stability. Bond strength and dimensional stability are retained across a wide temperature band rather than collapsing near the resin's softening point. Chemical resistance. Heat-stable backbones also resist solvents, fuels, oils, and many process chemicals. Mechanical strength. Shear and compressive strength stay high enough for structural bonding and potting under load. Formulation range. Grades vary in viscosity, cure schedule, filler loading, and flexibility to suit different substrates and processes. Advantages in High-Heat Service Bonds where conventional epoxy fails. Reliable joints in locations that a general-purpose adhesive cannot survive. Durability over many thermal cycles. Resistance to the repeated expansion and contraction that fatigues a bond line. Design freedom. Structural adhesive bonding becomes an option in hot assemblies where only mechanical fastening or welding was previously viable. Lower maintenance. Durable bonds reduce the frequency of repair and replacement in heat-exposed equipment. Sealing plus bonding. Many grades seal against gas and fluid leakage while carrying load. Applications Aerospace: bonding brackets, heat-shield hardware, and engine-adjacent components. Automotive and transit: exhaust-system components, turbocharger hardware, sensor mounting near hot zones, and brake-system parts. Electronics: potting and encapsulating components in high-power modules and lighting where junction and ambient temperatures are elevated. Oil and gas: downhole tool assembly and component bonding under combined heat and pressure. Power generation: bonding and potting in turbine, generator, and boiler-auxiliary equipment. Industrial process equipment: ovens, dryers, kilns, and furnace instrumentation. Choosing the Right Grade Confirm the real service temperature. Identify the highest continuous temperature and any transient spikes at the bond location. Select a grade rated with margin above that figure; running an adhesive at its ceiling shortens life sharply. Match the substrate and manage expansion. Metals, ceramics, and composites expand at different rates. A rigid high-temperature epoxy between two materials with very different expansion coefficients builds stress on every heat cycle. Our explanation of how CTE mismatch causes adhesive bond failure covers the mechanism and why a filled or slightly resilient grade can outlast a rigid one on mixed joints. Check chemical exposure. Verify resistance to the specific fluids and vapors present, and to any cleaning chemistry used in service. Plan the cure. Nearly all ultra high temperature grades need an elevated-temperature cure, often a staged ramp, to develop full properties. A room-temperature-only cure on these chemistries typically leaves the joint under-strength. Confirm the shop can deliver the schedule. Assess mechanical demand. Match the grade's shear and compressive ratings…

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May 7, 2024