CR39

CR-39 is a transparent thermoplastic polymer based on allyl diglycol carbonate (ADC) that is widely used for eyeglass lenses and as a solid-state nuclear track detector. The name CR-39 traditionally derives from Columbia Resin 39, the designation for the material produced by the Columbia Resin Company. The polymer is formed by polymerizing ADC monomer to produce a clear, glassy plastic with good optical quality.

Optical properties include a refractive index of about 1.498 to 1.50 in the visible range and an Abbe value around 58, contributing to relatively low chromatic aberration. It has a low density, good optical transmission in the visible spectrum, and can be polished to a high finish. It is relatively easy to mold and process, making it common for cast or molded lenses. It is generally less impact resistant than polycarbonate, but more scratch resistant with hard coatings.

UV and coatings: CR-39 lenses inherently block a substantial portion of ultraviolet light, but complete UV protection typically requires additional UV-absorbing coating or dopants, depending on formulation.

Usage: In ophthalmology, CR-39 is used to produce lightweight, affordable eyeglass lenses with good optical quality. In science, CR-39 is widely used as a solid-state nuclear track detector: charged particles create damage trails that can be chemically etched to reveal faint tracks, enabling measurements of particle range and LET for cosmic ray studies, dosimetry, and high-energy physics experiments.

Processing and safety: It is a thermoplastic; processed by extrusion, casting, or molding, then ground and polished for lenses. It is generally considered safe in handling; disposal follows standard plastic waste guidelines.