How do hot-melt adhesives work?

Hot-melt adhesives are a type of synthetic adhesive based on thermoplastic resins. These materials are designed to melt at elevated temperatures without undergoing degradation, allowing them to be applied as hot liquids to a surface.12

Once applied in this molten state, they function as fast-drying, nonvolatile adhesives. As they cool, they solidify to form a bond. Because they are thermoplastic, they can be softened by heating for application and do not form the permanent, insoluble bonds characteristic of thermosets.312

Commonly used polymers in these adhesives include polyamides, polyesters, polyurethanes, and various block copolymers or elastomers. While standard hot-melts are typically limited to use in temperatures between 40–65 °C (100–150 °F), manufacturers have developed structural hot-melts—modified with reactive or moisture-curable urethanes—to provide higher heat resistance and improved adhesion performance.1