Zyl - This is a term used for a variety of plastic materials used in making frames, the most common of which is Cellulose acetate. Cellulose acetate is made from a cellulose material extracted from cotton or wood pulp mixed with anhydride acetic acid, plastisizers and aging stabilizers. This material can be shaped into frames in two ways. It can be formed into sheets from which frames are stamped, or it can be injected into frame molds. It comes in a very wide range of colors with good color stability and is easily adjusted.
Some people have allergic sensitivity to zyl frames.
This is less likely with high quality zyl frames, which usually have an additional protective coating that prevents fading and UV damage to the frame material. Polycarbonate is also used for nonprescription shields, where the lenses and frame are molded in one unit. It is also the material used in the type of sports frames held on with elastic straps. In combination with polycarbonate lenses, this material offers optimum impact resistance and eye protection. This material can not be adjusted very well.