Waldo Lonsbury Semon was an American chemist who discovered how to plasticize PVC, a development that led to the widespread use of PVCs. Semon is also known for developed widely-used plastisol technology and many other innovations in plastics.

Born in Demopolis, Alabama, Semon graduated from the University of Washington with a BS in chemistry and a PhD in chemical engineering. He worked at B. F. Goodrich Company from 1926 until 1963, and for much of that time was director of research, leading teams that invented many types of plastics. Semon found the formula for vinyl, mixing synthetic polymers that resulted in a substance that was elastic, but not adhesive. He also worked on methods of improving rubber, and eventually developed a synthetic substitute. In 1935 he created Koreosol from salt, coke, and limestone, a polymer that could be made in any consistency. Semon made more than 5,000 other synthetic rubber compounds, also achieving success with Ameripol (AMERican POLymer) in 1940. In all, Semon held 116 patents.

Semon was awarded the Elliott Cresson Medal from the Franklin Institute in 1964. He was inducted into the Plastics Hall of Fame in 1982 and the Invention Hall of Fame in 1995.

See:

Waldo Semon article at Lemelson-MIT Inventor of the Week Archive,

Waldo Semon article in Wikipedia