What is the difference between plastic and polycarbonate?
The “standard plastic” lenses in safety glasses are often called “Hard Resin”, “CR-39 plastic”, or just “plastic” lenses. CR-39® is actually a PPG Industries registered trade name for a DADC (diallyl diglycol carbonate) polymer that was 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 “hard resin” or “CR-39 plastic” is a thermoset plastic meaning it cannot be molded or bent when heated. On the other hand, the polycarbonate polymers (e.g., Lexan®, a GE trade name) are thermoplastic which means that the lenses can be formed by melting polycarbonate pellets and injecting them into a mold. What should I know about the fit and care of safety glasses? If eye protection is required, establish a complete eye safety protection program including selection, fit testing,
