ABSTRACT
We can define hot-melt adhesives as thermoplastic materials, solid at room temperature. When heated above their melting point, they become fluid and are able to wet the surfaces to which they are applied. Generally, quantity of fluid hot melt is applied to one or both of surfaces to be joined, and the surfaces are brought together. One way to typify hot-melt adhesives is to distinguish by the backbone polymer. In some instances the polymer is used neat, but often other materials are incorporated to form the finished adhesive. Condensation polymers are formed by combining two or more monomers with the elimination of small molecules; for example, polyamides are formed by the reaction of organic acids and amines with elimination of water. As a rule the addition-type polymers require compounding to be useful as hot-melt adhesives. Typically, such a formulated hot-melt adhesive would contain the backbone polymer plus one or more of following: tackifiers, plasticizers, flow modifiers, antioxidants, pigments, extenders, etc.
