Those who use adhesives can easily fall into a misunderstanding: equating "adhesive viscosity" with "bonding strength" and confusing the two. Ultimately, the reason for this mistake is a lack of clarity about adhesive parameters. Today, we'll introduce you to adhesive viscosity and adhesive bonding strength, hoping to help you gain a deeper understanding of adhesive parameters and avoid detours in adhesive application

I. Adhesive Viscosity

Viscosity is an important parameter of an adhesive. It reflects the strength of the interaction between liquid molecules during movement and is a physical data used to measure the magnitude of viscous force. When a fluid is flowing, there is relative motion between adjacent fluid layers, and the frictional resistance generated between these two fluid layers is called viscous resistance. Simply put, for adhesives, viscosity is a reference value reflecting whether the adhesive is thin or thick. Generally, the thicker the adhesive, the slower its fluidity, indicating a greater adhesive force; conversely, the thinner the adhesive, the faster its fluidity, and correspondingly, the smaller the adhesive viscosity.

II. Adhesive Strength

The bonding strength of an adhesive, also known as the adhesive strength, is one of the important indicators for evaluating the quality of an adhesive. Bonding strength refers to the stress required to cause damage at the interface between the adhesive and the adherend or in its vicinity in a bonded part under the action of an external force. Moreover, according to the stress conditions during the use of the adhesive, the bonding strength is usually further divided into shear strength, tensile strength, peel strength, and impact strength, etc. The magnitude of the bonding strength depends not only on the adhesive force, the mechanical properties of the adhesive, the properties of the adherend, and the bonding process, but also on factors such as the joint type, stress conditions (type, magnitude, direction, frequency), environmental factors (temperature, humidity, pressure, medium), test conditions, and experimental techniques. It is worth noting that the adhesive force is only one of the important factors determining the bonding strength. It is a completely different concept from the bonding strength and cannot be equated.

The above is the introduction to adhesive viscosity and bonding strength. The two are essentially very different. So, dear friends, don't think that the higher the viscosity of an adhesive, the higher its bonding strength. Theoretically, the bonding strength does not have a fixed value. It must be considered in combination with the material of the adherend to be meaningful. Be sure to note: The actual bonding strength can vary greatly for adherends of different materials!
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