Technical Terminology for Adhesives

▶ Adhesion
The state in which the surfaces of two materials are held together by chemical forces, physical forces, or a combination of both.

▶ Adhesive
A substance capable of bonding adherends together through the process of adhesion.

▶ Cohesion
The state in which particles within a single substance are held together by primary and/or secondary valence forces.

▶ Adhesive failure
A visually apparent failure occurring at the interface between the adhesive and the adherend.

▶ Cohesive failure
A visually apparent failure occurring within the adhesive or the adherend itself.

▶ Compatibility
The ability of two or more substances to exhibit mutual affinity when mixed.

▶ Mechanical adhesion
Bonding between two material surfaces resulting from the interlocking action of the adhesive.

▶ Adherend
The object intended to be bonded.

▶ Substrate
The material upon which an adhesive is applied.

▶ Wetting
The affinity of a liquid for a solid; the smaller the contact angle between them, the more easily the solid surface is wetted by the liquid.

▶ Drying
The process of altering the physical state of the adhesive on the adherend by reducing the solvent or dispersion medium through evaporation or absorption.

▶ Bond
Joining the surfaces of adherends together using an adhesive.

▶ Curing
The process by which an adhesive acquires and enhances properties—such as bond strength—through chemical reactions (e.g., polymerization, cross-linking).

▶ Setting
The process by which an adhesive acquires and enhances properties—such as bond strength—through chemical reactions or physical processes (e.g., polymerization, oxidation, gelation, hydration, cooling, evaporation).

▶ Cross-linking
The process of forming chemical bonds between molecules to create a three-dimensional network structure.

▶ Adhesive layer
The layer of adhesive within a bonded assembly.

▶ Delamination
The separation of layers in a laminated product caused by failure of the adhesive, the adherend, or the interface between them.

▶ Squeeze-out
Excess adhesive forced out of the adhesive layer after pressure is applied to the assembly.

▶ Fillet
Adhesive filling the junction between two adherends (e.g., the rounded bead of adhesive formed at the end of a honeycomb core when bonded to a facing sheet).

▶ Degree of cure
A measure of the extent of the chemical reaction during the curing of an adhesive.

▶ Ageing
The phenomenon wherein the properties of a bonded assembly change over time.