Adhesives and sealants have been used for centuries, with the earliest adhesives and sealants being made of natural materials, such as tree sap, beeswax and tar. Later, processed natural products were used such as animal protein, resin, natural latex. 

With the emergence of the chemical industry and synthetic polymers, the range of adhesive and sealant formulations exploded. Today’s adhesives and sealants may be classified in many different ways, such as by cure (bonding) mechanism, chemistry type, and even application (e.g. structural vs. non-structural). 

A more in-depth discussion of the breaksdowns of adhesives, first by cure mechanism  - physically hardening, chemically curing and pressure sensitive - and then by chemistry, can be found on the following pages.

 Physically Hardening 

 Chemically Curing 

 Pressure Sensitive