Polymeric materials have several fundamental physical properties that are important in adhesion. These properties are controlled by the chemical structure of the base polymer from which the adhesive or sealant is made and from the various formulating agents used to modify the base polymer. This article will review one of the more important properties, the glass transition temperature, Tg, which is actually a composite of several physical attributes. We will examine the relationship that Tg has on cohesive strength, pressure sensitive adhesion, and certain application properties.
The structural characteristics of polymeric molecules that have been identified as affecting the physical properties of adhesives and sealants include molecular weight, composition of the polymer chain, functionality, polarity, chain structure, crystallinity, and crosslinking. These determine the physical properties of the adhesive or formulation including glass transition temperature, melting or softening point, surface energy, bulk and rheological properties, and stability.