Polycarbonate safety glasses
Polycarbonate (PC) is a crystal clear and colorless engineering thermoplastic known for its high impact resistance. PC was originally developed for the aerospace industry to be used in windows for airlines, space shuttles and face shields for astronaut helmets.
Polycarbonate is the most impact resistant lens material available today. When compared to glass or CR-39 Plastic, polycarbonate offers significantly greater protection and safety for your eyes.
PC is a very soft material and will not crack or break during an impact. In manufacturing PC an enormous amount of pressure is used to compress the raw material. It holds up well under impact because it is flexible and gives slightly under pressure without breaking. PC lenses are constructed out of material that is identical to what is called “bulletproof glass.”
Unlike regular glass and plastic eyeglass lenses, polycarbonate will not shatter upon impact or violent contact, thus preventing injury to the eye from the broken pieces. That is why polycarbonate lenses are recommended, not only for safety glasses, but for sports goggles and children’s glasses as well.
A word of caution: Although polycarbonate lenses have been tested to withstand objects thrown at a high rate of speed, they should not be tested while someone is wearing them. PC is impact-resistant, but there is no guarantee of non-breakage.
The disadvantage with PC is that it has a tendency to scratch easily. Thus, most lenses are treated with an anti-scratch coating.
Polycarbonate lenses are sometimes referred to as featherweight lenses because they are thinner and lighter in weight than the other types of lenses. This is because less of the polycarbonate lens material is requiredn to provide the same amount of visual correction that a traditional plastic lens needs.
PC is UV stabilized and, therefore, won’t dry out and become brittle after exposure to sunlight. UV protection shields the eyes from damaging light rays similar to the way that sunblock prevents the sun’s rays from damaging the body. Other types of plastic lenses must be treated to block the same amount of UV, but PC lenses automatically offer this protection. PC filters
out 99.9% of all harmful UV radiation. It has the ability to add UV400 absorber to give extra UV protection for use in environments with high levels of UV radiation. The UV400 lens with the UV absorber built into the material will not scratch off, and is therefore, the best protection. Lenses made of glass are not good UV filters.
The chemical resistance of PC is good while being used with diluted acids, alcohols, greases and oils.