In applications that have an exposure to solvents, acrylic conformal coating is not the best choice. Acrylic conformal coating can be removed with a weaker solvent such as isopropyl alcohol or xylene. Whenever it faces even stronger solvents, it will not offer the protection that is needed, especially if your product is a mission critical device. Other coatings, such as urethane or parylene conformal coating have a far better resistance to solvents than acrylics.
High temperature requirements
For products that require a high temperature application, acrylic conformal coating will fall short of expectations. For HumiSeal 1B31, arguably the most popular acrylic coating, the max continuous operating temperature is 125ºC. Compare this to silicone conformal coating, whose operating temperature can exceed 200ºC. For higher temperature requirements, silicone conformal coating will perform at a level that acrylics cannot.
For substrates that will face mechanical wear, acrylics will disappoint. While they do have a better mechanical wear resistance than silicones, acrylics fall behind urethane and epoxy conformal coating in this category.