Bulk hot melts are supplied in a variety of shapes including blocks, pellets, granules, and powders. They are packaged in sizes as small as one pound to 50 pound bags and pails to drums and totes. A range of applicators is also available depending on the volume output of adhesive needed for the assembly process. Some hot melt applicators consist of a heated reservoir to which solid adhesive is added. Molten adhesive in this reservoir is pumped through heated hoses to either handheld applicators or automatic applicator heads. Other applicators have a heated grid on which the solid adhesive is placed. The adhesive melts and flows through the grid into a small reservoir which holds a pump. For adhesives supplied as solid blocks in pails or drums, heated platens are available that melt the top few inches of adhesive that is in contact with the platen. An inlet in the center of the platen allows molten adhesive to flow into a pump. Handheld applicators at the end of the heated hose are used to dispensing adhesive in bead or spray. Automatic applicator heads can be used to dispense beads or ribbons in a variety of patterns or spray the adhesive for bonding large areas. Bulk hot melt adhesives can also be applied using a roll coater with heated rolls.
Bulk hot melts are formulated to match the needs of the application and assembly processes as well as the performance requirements of the bonded assembly. High speed, automatic assembly often requires lower viscosity and faster rate of strength build-up. Very large area bonding requires much longer open time (slower setting of the adhesive on cooling to allow wetting of the substrates).