What distinguishes hot melts from other adhesive types is that they are applied in their molten state (usually 175-205 degrees C), and then rapidly cooled to form a tough, adherent solid at room temperature. Their rapid set time, coupled with their relatively high viscosity, makes them ideal for bonding porous materials. Hot melts find numerous applications in a variety of manufacturing processes, including box and carton sealing, bookbinding, footwear, and labeling.
Hot-melt adhesives are applied in a molten state, and most must flow smoothly onto surfaces to ensure both wetting and adhesion. Thus, viscosity as a function of temperature is a key to proper hot melt performance. In addition, factors such as bond strength, flexibility, tack and set time are intimately related to the adhesive’s rheology. By knowing the rheological characteristics of a given hot melt, users can determine its suitability for a given task, or modify the formulation to customize it for a specific application.