What Does
Adhesive Strength Mean?
Adhesive strength refers to the ability of an adhesive to stick to a surface and bond two surfaces together. It is measured by assessing the maximum tensile stress needed to detach or unstick the adhesive perpendicular to the substrate.
The adhesive strength is the maximum tensile stress possible at the interface. It is affected by the coating thickness and the solvent retention, when solvent-containing coatings are used.
When an adhesive is bonded to an item or surface, numerous physical, mechanical and chemical forces come into play, which may affect each other.
Corrosionpedia Explains Adhesive Strength
Adhesive strength is the measurement of adhesion, or the attachment between adhesive and substrate. This may occur either by mechanical means, in which the adhesive works its way into small pores of the substrate, or by one of several chemical mechanisms.
The strength of adhesion depends on many factors, including the means by which it occurs. Methods of adhesion include:
- Chemical bond may occur between the adhesive and substrate.
- Electrostatic forces, as in static electricity, hold the substances together.
- Van der Waals forces may develop between molecules.
- Moisture-aided diffusion of the glue into the substrate, which is followed by hardening.
For example, pressure-sensitive adhesives (PSA) form a bond by the application of light pressure to seal the adhesive with the adherend. The bond forms because the adhesive is soft enough to flow to the adherend. The bond has strength because the adhesive is hard enough to resist flow when stress is applied to the bond. Once the adhesive and the adherend are in close proximity, molecular interactions, such as van der Waals forces, become involved in the bond, contributing significantly to its ultimate strength.
Some high-performance permanent PSAs exhibit high adhesion values and can support kilograms of weight per square centimeter of contact area, even at elevated temperatures. Removable adhesives have low adhesion and generally cannot support much weight.
Determination of the failure point can be critical for the final use of the material and the adhesive. There are a large number of different adhesive products, which require different testing methods to characterize the properties of the material.
Testing may be performed for quality control purposes, but is more typically undertaken to adhere to industry standards and customer specifications. Even in established coating application processes, many factors can influence the adhesive strength of a coating. Seemingly minor variations in process parameters may have significant impacts on the resulting adhesion strength between the coating and the substrate.