Plastic KAM snaps are made from polyacetal resin, a type of plastic that is stronger and more durable than other types of plastic. They can be heated in a microwave, such as in a situation when they are attached to a heating pad.
Do note that extreme heat may cause the snaps to expand slightly. If your snaps are securely installed, it shouldn't make a difference. But if they are on the verge of not being secure, then the slight expansion may result in the snaps not closing properly.
General guidelines from the factory state that the plastic snaps can withstand temperatures of 100 degrees C (about 212 degrees F) for up to 2 hours without becoming deformed. Note that snaps should never be placed over direct heat. Results may vary depending on different factors, so we recommend testing yourself under your specific conditions.