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The term CR-39 technically refers to the ADC monomer, but is more commonly used to refer to the finished plastic. The abbreviation stands for "Columbia Resin #39", which was the 39th formula of a thermosetting plastic developed by the Columbia Resins project in 1940.
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 ...
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.
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.
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 ...
The non-spherical curvature of an aspheric lens can also be created by blending from a spherical into an aspherical curvature by grinding the curvatures off-axis. Dual rotating axis grinding can be used for high index glass that isn't easily spin molded, as the CR-39 resin lens is.
In optics and lens design, the Abbe number, also known as the Vd-number or constringence of a transparent material, is an approximate measure of the material's dispersion (change of refractive index versus wavelength), with high values of Vd indicating low dispersion.
What does "39" refer in the cr-39 term? Is this still made in where you said by the company you said? Is it made anywere else in the world? PPG still makes CR-39 lenses, AOLite also makes tons of cr39 (as hard resin) lenses, it's a pretty popular optical material in eyeglass labs, and it could easily be argued, is optically superior to polycarbonate in many ways. It is definately made ...