Having worn glasses for over half of my life, I am very familiar with living through rectangular windows. Having to constantly adjust them on my face or being careful not to break them, I am familiar with all the little quirks that wearing glasses comes with, but I am not as familiar with the materials that lenses are made from. I called my ophthalmologist and found what lay across my face was actually polycarbonate.
What is polycarbonate?
The molecular structure of polycarbonate derived from BPA and phosgene.
Polycarbonate is an amorphous thermoplastic material utilized in various ways such as protective sheeting, electronic components, water bottles, light fixtures, windows, medical supply components, and eyeglass lenses. It is made from the polymerization of BPA and phosgene.
Polycarbonate is a naturally transparent, tough, ductile material that has a high resistance to impact but it is not a hard material. To protect from This makes it a great material for safety eyeglass wear.
CR-39 is the cheapest plastic used with a lower index of refraction. Polycarbonate falls in the family of high index plastics but has the benefit of being tougher and shatter proof than the others (Lenses RX).
Properties of PC
Polycarbonate has a 80-85% transmission of light (Ecologic Technologies).
The attraction between the different benzene rings of the molecule create a rigid structure giving the material it's impact resistance properties. The amorphous nature of the polymer gives it the optic properties that make it suitable as a lens (Polymer Technologies and Services). The thermoplastic aspect of PC makes it easy to work with by extrusion and molding.
Polycarbonate has a refractive index of 1.586 but when combined with Titanium dioxide at the expense of tensile strength and ductility (Kodak).