TECH SPOTLIGHT High Temperature Resistant Adhesives Beat the Heat Master Bond Inc. 154 Hobart Street, Hackensack, NJ 07601 USA Phone +1.201.343.8983 | Fax +1.201.343.2132 | [email protected]

High Temperature Resistant Adhesives Beat the Heat Too hot, too cold or just right? It’s not just a question for Goldilocks. Engineers have to be even better judges of temperature when they select a materials system for the job at hand. And those jobs increasingly involve temperature conditions that are best described as “extreme.” It’s no longer uncommon for aerospace, oil-and-gas, industrial and some electronics applications to require materials systems that withstand temperatures of 300°C or greater. Other applications have to contend with extreme cold, even down to cryogenic temperatures...

With a couple of important exceptions, adhesives with the best heat resistance tend to have high Tg values, making them rigid across their operating temperature range. Epoxies used to be unmatched in this regard with some grades offering Tg of 230°C and service temperatures up to 315°C. Master Bond’s newly developed bismaleimide adhesive (see sidebar) ups the ante on heat resistance substantially with a Tg of 300°C and predicted service temperatures in excess of 340°C. The exception to this relationship between heat resistance and a high Tg involves some silicones and “B-stage epoxies”. The unique...

This ability to work in environments that mix extreme heat and cold is particularly important in aerospace applications. Adhesives with a low Tg that function just fine in a purely cryogenic environment tend to exhibit large CTEs as they heat up–with all the thermal stress problems that large CTEs can imply. High Tg adhesives tend to have smaller, manageable CTEs across their entire operating temperature range, and may be more suitable for these mixed extreme environments. Managing Minor Trade-offs The good news about temperature resistant adhesives is that they offer a balance of properties...

POPULAR MASTER BOND HIGH TEMPERATURE RESISTANT APPLICATIONS Two Component Epoxies — Mix Ratio by weight Color Code Mixed Viscosity RT, cps Set-Up Time Minutes, RT Cure Schedule Temp/Time, °F Service Temp Range, °F 100/100 “A” clear “B” amber 100,000120,000 60-90 48 hrs @ RT 2-3 hrs @ 200°F -100°F to +350°F Toughened system is well suited for bonding & sealing of dissimilar substrates. Thermal cycling. EP30HT 100/25 “A” clear “B” clear 35,00045,000 25-35 24 hrs @ RT 1-2 hrs @ 200°F -60°F to +400°F Transparent system with superb physical strength, chemical resistance, and electrical insulation...

MEASURING GLASS TRANSITION TEMPERATURE THERMO MECHANICAL ANALYSIS CTE “Vitreous” “Rubbery” Tg Temperature DIFFERENTIAL SCANNING CALORIMETRY Heat Capacity “Vitreous” “Rubbery” Tg Thermoset adhesives, such as epoxies, do not melt before degrading in the way that thermoplastic materials do. Instead, these adhesives undergo a state change as they heat to a point known as the glass transition temperature (Tg). Above the Tg, the adhesive remains in a rubbery, more ductile state. Below the Tg, the adhesive becomes increasingly strong yet more brittle. The graphs here show how lab methods can determine...