Hot melt

A hot melt adhesive is a thermoplastic material, solid at room temperature, which is applied in its molten form and will adhere to a surface when cooled.

The wax is used as an additive in hot melt adhesive composition, which is used in bonding articles such as those made from fibrous cellulosic materials, plastic, wood, metal, etc.

A Brief History of hot melt

When some natural materials fell on rocks heated by the sun, they softened and became sticky, and later hardened in the cool of the night. Observers made use of these natural phase-change materials as they chanced upon them. When lightning started fires some materials melted and then cooled in interesting shapes. Observers, using the fires to harden their sharpened stick weapons, put out the fires by rubbing their sticks on the ground, and some contacted and melted resins, which when cooled, again hardened. Thus was born the technology we now call hot-melt adhesives.

Hot melt properties

All the thermoplastics adhesives require heating in order to melt the polymer, hence the name “hot-melt”. The time a hot melt adhesives takes to solidify to a point where it can no longer bond is called the ‘open time´. The time required for the adhesive to cool to the point where is has enough strength to form a bond is the ‘set speed´. These properties are optimized with the addition of waxes and resins with certain properties. The low viscosity of the wax is used to reduce the high viscosity of the polymer and resin to ensure efficient mixing. This reduction in viscosity is particularly important during the application stage. A low viscosity is required to pump the molten adhesive from the storage tank to the application area and to ensure proper surface wetting when applied