Adhesives Technology Review
Appendix F

GLOSSARY OF TERMS

Adhesion
The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking action.

Adhesion, Mechanical
Adhesion between surfaces in which the adhesive holds the parts together by interlocking action.

Adhesive, Specific
Adhesion between surfaces which are held together by valence forces or molecular bonding.

Adhesive
A substance capable of holding material together by surface attachment.

Adhesive Failure
Failure resulting from insufficient bonding between the adhesive and one or both substrates. Adhesive strips away from substrates.

Adhesive Tensile
An adhesive is in tensile loading when the acting forces are applied at right angles to the plane of the adhesive. The tensile strength of a bond is the maximum tensile load per unit area, required to break the bond expressed in pounds per square inch.

Cohesive Failure
Occurs when internal strength of the adhesive is not as great as the forces applied to it. Adhesive remains bonded to both substrates.

Cure
The mechanism or chemical reaction by which an adhesive’s physical properties are changed from the state in which it was applied to a surface to the state in which it forms a strong bond. This process may require the application of heat and/or pressure, or the presence of a catalyst.

Degradation
Deleterious change in the chemical structure of a plastic reflected in its appearance or physical properties.

Emulsion
A stable dispersion of immiscible liquids, one of which is water.

Film Tension
The greatest longitudinal stress a cast film (125 mils thickness) can bear without tearing apart.

Flow
The movement of adhesive during the curing stages before completely cured.

Heat Resistance
The temperature at which a bond subjected to a pounds per square inch (PSI) load fails.

Hot Tack
A characteristic of hot melts, in which they have holding power even while in the liquid hot state.

Latex
An adhesive that is a colloidal dispersion of solid polymer particles in water.

Mechanical Adhesion
Adhesion between surfaces in which the adhesive holds the parts together by interlocking action.

Penetration
The entering of an adhesive into a substrate.

Photoinitiator
A compound that forms reactive species which will initiate chain reaction to cause polymer formation when exposed to specific wavelengths of energy.

Polymerization
A chemical reaction in which two or more small molecules continue to form larger molecules that contain repeating structural units of the original molecules.

Pot life
The length of time an adhesive remains usable after it has been prepared for application.

Sag
Occurs when there is excessive flow in material after application to a surface.

Set
Applies to adhesives that develop their final form by means other than polymerization. Adhesives can set by evaporation of a solvent or water, or by hardening upon cooling to room temperature.

Shear strength
The measurement of the adhesive to withstand a force applied parallel to the cross-sectional area of the material.

Shear tensile
An adhesive is in shear tensile loading when the acting forces are applied parallel to the plane of the adhesive. The tensile strength of an adhesive bond is the maximum tensile load per unit area required to break the bond. Expressed in pounds per square inch.

Shelf life
The length of time that an adhesive, in its packaging, can be stored before use and remain usable for its intended purpose.

Tack
The ability of an adhesive to form a measurably strong bond immediately after the adhesive and substrate are brought into contact using low pressure. Also described as the initial adhesion, stickiness, or quick grab.

Thermoplastic
A material capable of being repeatedly softened by heat and hardened by cooling.

Thermoset
A material that will undergo a chemical reaction driven by heat, catalysts or other mechanisms, and leading to a relatively infusible state.

Viscosity
The measure of the resistance of a fluid to flow usually expressed in poise (or centipoise). A higher reading indicates more viscous material.

Wetting
The ability of an adhesive to adequately wet the surfaces of the substrates and subsequently "set" or harden to form a strong bond. Good wetting requires that the adhesive flows over the entire surface, filling crevices and cracks.

Return to the introduction of the Hot Melt Adhesives Technology Review.

Return to the introduction of the Radiant-Cured Adhesives Technology Review.

Return to the introduction of the Waterbased Adhesives Technology Review.