Classification of Adhesives Based on Chemical and Physical Appearances

Adhesive is whichever substance which is able in holding two or more than two supplies together in a functional way by face attachment which resists separation. Many examples can be considered as adhesives together with cement and glue.

Adhesives may be classified in various ways, for instance, by chemical nature or physical form which is relatively strong in forming the bonds, or by mechanism of cure. For many purposes, this last is the mast useful, since, with one notable exception, every adhesive has to pass through a phase transition in the course of its use. This change will involve one of three general process:

1. Loss of solvent or dispersant
2. Solidification by cooling
3. Chemical reaction

In addition, there is one group that retains a liquid state, even if extremely viscous, throughout their usual life. Thus, adhesives are solvent based, hot melt, reactive, and pressure sensitive. Within each of these adhesives (but particularly the "reactive"), there are subdivisions corresponding to the particular chemistry involved.

While it is usual practise to describe an adhesive, particularly reactive adhesives, by the broad chemistry involved, it is important to recognize that all industrially satisfactory adhesives contain a range of additives to modify various properties such as viscosity, stability, tack, and gap filling). Thus, one very common one, which is apparently a simple solution of a single polymer, polychloroprene, in an organic solvent, actually contains a second polymer, a mixed solvent, a trackifying resin, a neutralizing agent, and an inert filler, at least; however, it is still usually referred to as a polychloroprene adhesive.