Safety Glasses - Pyramex, Uvex & Willson

Polycarbonate
Essentially all Safety Glasses today have their lenses made from polycarbonate. About 30 years ago, when I first started selling safety glasses, lenses made from heat treated safety glass were predominant. This special heat treating was used to increase the ability to resist impact. There were several drawbacks to this technology. First was weight, with even the standard 48mm 'Buddy Holly' style glasses being quite heavy. Next was style, and how to make shapes that would be acceptable to workers that were starting to use sport glasses at home. Then came cost, with standard safety glasses costing anywhere from $6-$12 (in 1978 dollars!) due to the many hand labor operations involved. Lastly, and perhaps most important, lenses made with safety glass have a much lower resistance to impact vs polycarbonate. Even small scratches in a glass lens would release some of the built-in tension from the heat treating, reducing even further their strength.

In general, polycarbonate (PC) is a crystal clear and colorless engineering thermoplastic notable for its high impact resistance. PC was originally developed for aerospace industry for use in windows for airliners, space shuttles and face shields for astronaut helmets. PC is a relatively soft and flexible material allowing it to absorb energy from an impact and not crack or break. The drawback to this feature is it’s tendency to craze or scratch easily. Therefore virtually all lenses we sell are treated with an anti-scratch coating. PC is exceptionally light weight, making it an almost ideal material for the lens in a pair of safety glasses. While PC is sometimes used in the frame as well, these are generally made from nylon, with the recent addition of rubberized surfaces for added comfort.

Primary Properties
Optical characteristics:
Light transmission 88.0 % (astm d 1003)
Haze 1.0 (astm d 1003)
Refractive index 1.586 (astm d 542)

PC is UV stabilized, and so won’t dry out and become brittle after exposure to sunlight

Filters out 99.9% of all harmful UV radiation