White Paper: Materials
High Temperature Resistant Adhesives Beat the Heat
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Selecting the right adhesive product for extreme temperature applications may seem as straightforward as reading temperature resistance values on data sheets. Some engineers will sometimes address temperature issues by simply selecting an adhesive rated for temperatures beyond their application's expected operating temperature. However, because suppliers test adhesives so differently, temperature resistance values on data sheets are notoriously inconsistent. Master Bond's latest white paper takes a closer look at some of these crucial issues and the key factors to consider when your adhesive application must beat the heat or cope with the cold.
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Overview
This Master Bond whitepaper focuses on high temperature resistant adhesives and their critical role in extreme environments such as aerospace, oil-and-gas, industrial, and electronics applications. These environments often expose materials to a wide temperature range—from cryogenic levels near 4K to well above 300°C. Selecting the right adhesive for such extremes requires deeper understanding beyond simple data sheet temperature ratings, which can be inconsistent due to varied testing methods.
A key concept explored is the glass transition temperature (Tg), an intrinsic thermal property of thermosetting polymers like epoxies, silicones, and bismaleimides. Tg marks the transition from a rigid, glassy state below Tg to a more ductile, rubbery state above it. Adhesives with higher Tg generally exhibit better heat resistance, maintaining tensile strength and manageable thermal expansion, which is crucial to reduce thermal stresses in applications. However, there are exceptions, such as some silicones and B-stage epoxies, which have lower Tg values but still provide good thermal performance and flexibility for thermal cycling.
The paper advises against overly conservative safety margins that push designers to select adhesives with unnecessarily high Tg, which can complicate curing processes (from room temperature cures to oven cures) and produce brittle adhesives less suited for thermal cycling. Duration of exposure is also important; short-term exposures above Tg may be acceptable, but extended periods demand adhesives with higher thermal stability.
Master Bond offers a broad portfolio of high temperature adhesives, including one- and two-component epoxies and silicones, suited for applications with continuous service temperatures ranging from cryogenic lows (4K) to highs exceeding 500°F and Tg values upwards of 300°C in bismaleimide systems. The company provides data on specific grades detailing viscosity, cure schedules, and service temperature ranges, highlighting specialized formulations for applications demanding biocompatibility, thermal conductivity, electrical conductivity, or cryogenic performance.
Laboratory methods such as thermomechanical analysis and differential scanning calorimetry are used to measure Tg by detecting changes in thermal expansion coefficient or heat capacity, providing reliable indicators of adhesive heat resistance.
In summary, this document underscores the importance of understanding Tg and adhesive chemistry when selecting high temperature adhesives, balancing heat resistance, mechanical properties, and processing requirements to ensure reliability in extreme thermal conditions.