Semon put his name into the history books for inventing vinyl, the world's second most used plastic. He found the formula for vinyl by mixing a few synthetic polymers, and the result was a substance that was elastic, but wasn't adhesive. In all, Semon held 116 patents, and was inducted into the Invention Hall of Fame in 1995 at age 97.
Semon is sometimes credited with inventing bubble gum, but this is inaccurate. He did invent a indigestible synthetic rubber substance that could be used as a bubble gum (and produced exceptionally large bubbles), but the product remained a curiosity and was never sold.