Hot melt adhesives are also known as hot glue and are a form of thermoplastic adhesives. They usually consist of one base material with various additives and are formulated to have a glass transition temperature and are available in clear, translucent, colorless, straw-colored, tan or amber. Pigmented versions are also available. The melt viscosity and the crystallization rate can be tailored for a specific application. Hot melt provides several advantages over solvent based adhesives; volatile organic compounds are reduced or eliminated and the drying or curing step is eliminated. Hot melt has a long shelf life and does not lose thickness while solidifying. Their high melt flow index makes them easy to apply.
Hot melt adhesives are versatile and are applied by extruding, rolling or spraying; the high melt viscosity makes them ideal for porous and permeable substrates. Hot melt is capable of bonding various different substrates including: rubber, ceramic, metal, plastic, glass and wood.
Resistance to water and solvents is critical in certain applications; textiles require resistance to dry cleaning solvents, permeability to gases and water vapor may be an issue and non-toxicity of all materials and additives plus odorless requirements are a necessity for food packaging.