What is the difference between CR-39® and polycarbonate lenses?
A. CR-39 is a PPG Industries registered trade name for diallyl diglycol carbonate (DADC) polymer, introduced in 1941. The “CR” stands for Columbia Resin and CR-39 was the 39th batch or formula made by Columbia Laboratories in Ohio. This polymer is a polycarbonate, but its starting materials are different from the resins used in safety glasses with polycarbonate lenses. The CR-39 is a thermoset plastic, meaning it cannot be molded or bent when heated. The polycarbonate polymers used in most safety glasses are thermoplastic, which means the lenses are formed by melting polycarbonate pellets and injecting them into a mold.
