Adhesion strength of adhesives
Adhesives provide greater bond strength compared to welding and mechanical joints, without reducing the strength of the subsurface or shell. To choose the right glue for your application, you must consider many factors. Knowing the adhesive strength and how to measure it will help you in choosing the right adhesive.
The adhesion strength of adhesives is measured using three tests; Tensile strength test, shear strength test and peel strength test, which all determine the effectiveness of the adhesive and the ability to stick to the desired subsurface.
Scientists investigate different adhesion mechanisms to determine the adhesive’s ability on different surfaces. Measuring the “adhesion efficiency” for a joint help determine the strength of a bonded assembly. The common way to measure this parameter is to separate the bonded joint with proportional force. The force required to separate the bond helps engineers gain a better understanding of adhesive performance in various applications.
The strength of the interfacial tension between the adhesive and the subsurface is usually the most important parameter in the design of an assembly with an adhesive connection. However, adhesion strength is not the only factor to create a perfect bond. Even if you use the strongest adhesive in the world, if the adhesive doesn’t bond well with the substrate, the bond will fail.
Adhesion Strength (internal adhesion)
It is the internal strength of an adhesive – in other words, it is the adhesive’s ability to withstand pressure. The higher the adhesion strength, the stronger the adhesive. Bonding strength is determined by the chemical composition of the glue. The strength of adhesives is in a wide range; From pressure sensitive adhesives to structural epoxy and acrylic adhesives. It is very important to know the type of stresses that act on the connection. Common stresses include shear, peeling, bending and tension. It is important to know the amount and frequency of stresses applied in the connection, in choosing the glue with the best connection strength.
It is a physical property of the subsurface that determines whether the adhesive makes substantial contact with the subsurface or not.
In a material with high surface energy, the liquid (glue) penetrates the surface and wets the surface; In matter with low surface energy, the liquid resists penetration and becomes a droplet.
The adhesive must be spread over the subsurface for proper bonding. To choose the right adhesive, it is very important to know the energy of the surfaces in the assembly and how it spreads on the subsurface. Surface cleanliness must also be considered as some adhesives require a high degree of subsurface cleanliness.