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CR-39 is now a trade-marked product of PPG Industries. [2] An alternative use includes a purified version that is used to measure ionising radiation such as alpha particles and neutrons. Although CR-39 is a type of polycarbonate, it should not be confused with the general term "polycarbonate", a tough homopolymer usually made from bisphenol A. [3]
The first contact lenses were made of glass, in 1888. Initially the glass was blown but soon lenses were made by being ground to shape. For the first fifty years, glass was the only material used. The lenses were thin, yet reports of injury were rare. In 1938 perspex (polymethylmethacrylate, or PMMA) began to replace glass in contact lens ...
Lenses sold in the US must pass the Food and Drug Administration ball-drop impact test, and depending on needed index these seem to currently have "best in class" Abbe vs Index ( N d): Glass (2× weight of plastics) or CR-39 (2 mm vs. 1.5 mm thickness typical on newer materials) 58 @ 1.5, Sola Spectralite (47 @ 1.53), Sola Finalite (43 @ 1.6 ...
Eyezen – Digitally surfaced lens marketed towards users of electronic devices; Xperio – Polarized sunglass lens; Optifog – Fog resistant lens technology; Stellest – Lens targeted towards young children, designed to slow the progression of myopia. Orma – Essilor's branding of the CR-39 lens material.
CR-39 (CR for "Columbia Resins" and 39 denoting it as the 39th polymer) had qualities suitable for plastic lenses, making it the most noteworthy of the polymers. [6] CR-39 is commonly used in the manufacturing of plastic eyeglass lenses.
This is nominally a result of the material used to produce the lenses: Although relatively durable inside of frames, CR-39 lacks impact resistance and cannot absorb the wear and tear of constant stress to the lenses caused by putting on, wearing, and removing glasses. [4] Rimways fare much better with CR-39 because the arches absorb shock and ...
CR-39 is the most common plastic lens, due to low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation. SR-91 is a proprietary material that was introduced by Kaenon Polarized in 2001. Kaenon's lens formulation was the first non-polycarbonate material to pass the high-mass impact ANSI Z.87.1 testing.
The material is a polymer, CR-39 sometimes advertised as "organic glass". Cokin produce various differently-sized versions of the Creative Filter System. The smallest is "A" ("Amateur", 67mm wide). The larger "P" ("Professional", 84mm wide) system covers cases where "A" filters are too small to cover the lens (or would cause problems at wider ...