Hot melt adhesives are thermoplastic materials, which simply means they are solid at room temperature, and form a tacky liquid when heated up, typical temperatures are 160°C to 180°C , hence the HOT in hot melt! These adhesives are widely used in
many industries such as packaging, labelling, product assembly, and bookbinding. They can be applied in a variety of ways, but perhaps the most common way is for the adhesive to be heated in a tank and then pumped under pressure through a nozzle, commonly known as jetting. Other methods include extrusion, slot coating, daubers, and wheel in pot applicators.

Hot melt adhesives come in a wide variety of formulations and formats suited to the individual application or end use conditions. There are four main ingredient types
used in any formulation: polymer, resin, wax or oil and anti-oxidant

Usually the type of hot melt is described using the main polymer type; EVA, rubber or polyolefin based. In general the different polymer types do not mix well so make sure to avoid doing this! Polymers give the guts or backbone to the adhesive and have an impact on the viscosity of the adhesive.

Resins are generally either natural or petro-chemical based. Natural resins are harvested from trees, ie Gum Rosin harvested from trees in China and as crude oil is turned into petrol, some of the by-products are then formulated into resins. The resin influences how sticky or cohesive the adhesive will be, and how well it will stick to different materials.

The wax or oil is used to reduce the viscosity of the adhesive making it easier to apply. Waxes make the final cold adhesive non-sticky and oils make the cold adhsive pressure sensitive.

Anti-oxidants play a vital role in prolonging the thermal stability of the hot melt adhesive by 'soaking-up' the oxygen that causes the degradation. Anti-oxidants can not eliminate degradation, but they drastically slow it down.