Factors That Can Affect Chemical Resistance in Adhesives
A standard question that many manufacturers ask our technical staff is, "How do your adhesives stand up to certain chemicals?"
Seems simple, right? Based on the chemical used, there should be a standard answer to follow. Well, it turns out this question is far more complex than people think.
There are many factors that determine chemical resistance. Once they are understood, a manufacturer can work closely with their customers to determine the best adhesive to recommend. Factors to consider are:
1. The chemical resistance must be tested in the actual bond configuration where the adhesive will be used. Example: Interfacial bonds will be more resistant than an adhesive exposed directly to the chemicals.
2. The temperature of the chemicals. Example: A bath of sulfuric acid at 80°C is more aggressive than one at 25°C.
3. The concentration of the chemical solution. Example: A higher concentration of sulfuric acid is more aggressive than a lower one.
4. The type and length of exposure. Example: A splash or wipe is less aggressive than a soak. The length of exposure to the chemical will also yield different results.
5. The adhesion of the specific adhesive to the substrates. Example: If you were to test the resistance of an adhesive to a specific chemical when bonded to polycarbonate it may pass. If you take the same adhesive, same chemical, and a different substrate, such as polyethylene, it may fail miserably in this same scenario.
6. The chemicals the adhesive will be exposed to. Example: A product may do better withstanding ammonia and water, than potassium hydroxide and water.
7. The polarity of the chemicals. Example: Acrylated urethanes withstand non-polar materials better than polar materials. In general, it is difficult to predict the outcome of an adhesive’s chemical resistance without specifically testing the adhesive on the customer’s parts, through their process, using their curing equipment. However, understanding the factors that may affect the adhesive’s resistance, can ultimately lead to a better adhesive recommendation for the customer.