Wednesday, April 23, 2008
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Polycarbonate is the most commonly used material to make lenses. Many of the top brands (Oakley, Rudy Project, Uvex, etc.) use it in at least some of their models. Basically, polycarbonate is a fancy word for plastic, but not your average plastic. The reasons for its usage are many. It definitely sounds a lot better than "plastic", especially when you are talking about sunglasses. It at least sounds stronger.
(For the chemists among us)
But this is far from the reason that many brands use polycarbonate for their lenses. The main reasons are that it is impact resistant, transparent, thermally stable (won't burn easily), lightweight and perhaps most importantly, UV resistant.
All of these reasons can account for their popularity in sunglasses, but impact resistance is especially important for sports sunglasses. In the case of extreme sports, impact resistance can be the difference between an eye injury (or worse) and broken lenses. This is an advertising point for a lot of brands actually, and a lot of them have really fancy (i.e. over the top) names for lens materials, most of which are polycarbonate.
Transparency and the ability to manipulate the color of lenses make polycarbonate a substance for use in sports and fashion eyewear.
UV resistance is the key reason for polycarbonate being used in sunglasses in general. Over time, UV rays can harm your eyes and cause irreparable damage. Sunglasses are first and foremost for protection, and polycarbonate itself blocks UV, no extra coatings or treatments are needed, making it ideal.
Scratching is a problem with polycarbonate, and one of its only weaknesses. It is resistant to scratching, but not to a great extent. If you put your sunglasses through a really good end-over-end spill, your lenses (and probably your spine) are going to be rough looking after. This is made worse ten fold if you have mirrored lenses, which I'll talk more about in the future. This is one of the places where glass lenses have an advantage, being a lot less likely to get scratched for minor drops.
If you are going to buy sunglasses, whether it be for fashion or sports, make sure your lenses are at least made from polycarbonate. Do not trust other plastics. Be especially careful when buying fashion sunglasses, as they often use cheaper plastics to save cost.
This post was written by: Sunglasses Guy
The Sunglasses Guy is a shallow but driven blogger who knows the ins and outs of the eyewear industry. Get ahold of him via e-mail or his Twitter