(hint #1) Being able to play whatever I want has been a central theme to my own discovering how to play guitar. I've been on that path for 37 years, and it's enabled me to uncover, test and refine a unique, skill generating learning approach.
It is important to note that urethane foam is most commonly used to refer to a material made from polyurethane. The urethane reference in this name is to the type of links, also known as carbamates, that join the units in polyurethane.
This will not happen to urethane primers. Urethane and Epoxy primers are activated and go through a thermosetting stage. Again, to simplify the answer, Thermosetting in this circumstance is an activated resin that is used in urethane primer becomes a plastic type finish.