Testing Adhesives for Resistance to Acetone

Many Master Bond epoxy systems are formulated with superior chemical resistance. In the lab, we continually test our materials by exposing them to specific chemicals over a long period of time. A common way of testing the chemical resistance of an epoxy is immersing a sample in a chemical and measuring its change in weight over time. A significant loss or gain in weight would indicate a decreased ability of a material to stand up to chemical exposure. These tests allow us to more accurately recommend the right adhesive based on specific application requirements.

In this experiment, we focused on testing our epoxies for their resistance to acetone. The compounds Master Bond used for testing are a variety of two component epoxies and one component UV curing systems with good overall chemical resistance. These were EP41S-5, EP41S-1HT, EP41S-5LV, EP62-1HT, EP46HT-2AO Black, UV25 and UV 26. A few thin castings, roughly 2 inches in diameter and around 0.125 inches thick, were made for each product and cured in accordance to their specifications. Once the cured samples were created and initial weight was recorded, we submerged them in acetone. Then we continued recording weekly weight measurements. We carried on these tests with weekly weight recording for varying lengths of time based on the products performance. Below you will see the results for soaking results for around 10 months in the first batch, 2 years for the next batch, and greater than 2.5 years for the 3rd batch of products. The castings were weighed periodically and the graphs shown below demonstrate the percentage of weight change over time.

To add perspective to these numbers (or, “For the purpose of comparison”), please notice that for each testing timeframe, a casting of a standard epoxy was also tested under these same conditions which served as a reference. As you can see in the graphs, the standard epoxy was not as resistant to the acetone as the other epoxies tested, demonstrating a significantly greater change in weight over time.

In general, a swelling of less than 4-5% can be considered excellent, especially since this test may be more rigorous compared to actual service conditions. It is also worth noting that in the context of a bonded joint or a potted assembly the exposure to acetone might not be as severe or direct, as in the above test conditions.

Please note, when choosing an epoxy for an application where the resistance to acetone is critical, many other factors must be considered in addition to the chemical resistance. Each of the epoxies in the chart above offers a distinct set of performance properties. For example, if thermal conductivity and high temperature resistance are needed, EP46HT-2AO Black may be a good option. If a fast cure is required and there is full access to a light source with no shadows, UV25 can be considered. For longer term exposure to acetone over several months to a year or longer, the likes of EP41S-5, and EP62-1HT are excellent candidates. They all need to be processed or cured differently and although some of them can be cured at room temperature alone, for enhancing/optimizing chemical resistance especially to acetone, it is critical to add heat.

Disclaimer: The findings in this article are not meant to be used for specification purposes.