How do you determine the quality of pressure-sensitive adhesive?

Take organic pressure-sensitive adhesives as an example: the quality of a pressure-sensitive adhesive can be evaluated from five aspects: adhesion strength, drying speed, viscosity, solid content, and pH value.

 

① Adhesive strength

Pressure-sensitive adhesives and pressure-sensitive adhesive tapes must first possess sufficient bonding strength to firmly adhere the bonded materials and meet specific application requirements. To determine whether the bonding strength of a pressure-sensitive adhesive or adhesive tape meets industry standards, one can pull apart two adhered materials along the bonding interface. If the adhered materials themselves are damaged after being pulled apart, it indicates that the bonding strength is adequate. However, if only the bonding interface separates without any damage to the adhered materials, it suggests that the adhesive’s bonding strength is insufficient.

② Drying speed

When selecting pressure-sensitive adhesives, choose the appropriate adhesive based on the bonding process. If the product is not suitable for the specific process, you can dilute the pressure-sensitive adhesive with a solvent. In most cases, the adhesive can be used directly; however, for production lines that rely on high-speed machine application, it’s common to use a diluted solution, which facilitates smoother coating. At the same time, methods such as baking or heating in tunnel ovens are employed to accelerate solvent evaporation, thereby reducing time and costs.

③ Viscosity

Viscosity is the most important factor affecting the quality of adhesives. If the viscosity is too high, the coating will be thicker, adhesive consumption will increase, drying will slow down, and the adhesive’s ability to wet and penetrate the surface of the substrate will be impaired, directly affecting the bond strength. On the other hand, if the viscosity is too low, the coating will be thinner, drying will occur too quickly, and problems such as poor adhesion are likely to arise.

④ Solid content

It is also one of the important factors affecting the quality of pressure-sensitive adhesives. The higher the solid content, the stronger the adhesive force and the faster the drying speed. Solid content also directly influences the viscosity and drying speed of pressure-sensitive adhesives.

⑤ pH value

Synthetic resin adhesives are generally weakly acidic and do not negatively affect bonding processes. However, waterglass and starch-based adhesives have relatively high alkalinity. Excessive alkalinity can not only corrode operators and equipment but sometimes also corrode the materials being bonded, leaving unsightly stains. Therefore, when purchasing adhesives, it is important to consider the impact of pH value on the product.