Frame materials should be light, strong and easily adjusted, but retain their shape well. They need be flexible enough (under under the right conditions) to insert a lens, inert both to external agents and body fluids, and be cosmetically attractive (e.g. colours, surface finish, retention of surface finish). No material can meet all these requirements perfectly however and so frame manufacturers are working hard to keep up with lens technology to provide us with the best choices of features and benefits for both function and fashion. As newer materials are introduced, there is an ever growing choice for every patient, from the person looking for lightweight simplicity, to the sports participant in need of increased flexibility, safety and fit.
There are two basic types of plastics – thermoplastics which can be re-formed with heat and those which can’t be, commonly called thermosetting. Almost all plastic spectacle frames are made from plastics which soften with heat, although they are not all thermoplastic. Frames are occasionally made from nylons or from composite materials, most of which do not soften properly on heating, although they may be thermoplastic.
This is probably the most common plastic spectacle frame material. It is tolerably light & strong, mechanically stable at normal temperatures, easily worked and relatively inert. It tends to whiten (this may be additives leaching from it) where in contact with body fluids, particularly at the bridge and temples. Acetate frames are often c