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The abbreviation stands for "Columbia Resin #39", which was the 39th formula of a thermosetting plastic developed by the Columbia Resins project in 1940. [ 1 ] The first commercial use of CR-39 monomer (ADC) was to help create glass-reinforced plastic fuel tanks for the B-17 bomber aircraft in World War II, reducing the weight and increasing ...
Polycarbonate lenses also protect the eye from UV light. Many kinds of lenses are manufactured from polycarbonate, including automotive headlamp lenses, lighting lenses, sunglass / eyeglass lenses , camera lenses , swimming goggles and SCUBA masks, and safety glasses/goggles/visors including visors in sporting helmets/masks and police riot gear ...
Plastic lenses are lighter and shatter-resistant, but are more prone to scratching. Polycarbonate plastic lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 is the most common plastic lens, due to low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation.
Plastic lenses are currently the most commonly prescribed lens, owing to their relative safety, low cost, ease of production, and high optical quality. The main drawbacks of many types of plastic lenses are the ease by which a lens can be scratched, and the limitations and costs of producing higher-index lenses.
Example of ballistic eyewear that can be made with prescription lenses (from U.S. Army APEL [1] list). Another example of ballistic eyewear from the U.S. Army Approved Protective Eyewear List (APEL). [1] Safety glasses, sunglasses and goggles that claim to meet ballistic safety standards are widely available. Some can accommodate prescription ...
A photochromic eyeglass lens, part of the lens darkened after exposure to sunlight while the other part remained covered. A photochromic lens is an optical lens that darkens on exposure to light of sufficiently high frequency, most commonly ultraviolet (UV) radiation. In the absence of activating light, the lenses return to their clear state.