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Why are hot-melt adhesives usually limited to uses below about 40 to 65 °C?
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adhesive
Overview of how glue and other adhesives work.
Hot-melt adhesives are primarily composed of thermoplastic resins. Because these materials are designed to melt at elevated temperatures without degrading, they inherently lack high-temperature strength.
This characteristic limits their effective use to temperatures between approximately 40 and 65 °C (100–150 °F), as the adhesive may soften or lose its structural integrity if exposed to heat beyond this range. To address this limitation, manufacturers have developed structural hot-melts, which are modified with reactive components like moisture-curable urethanes to improve heat resistance.1