Polycarbonate is a versatile, tough plastic used for a variety of applications, from bulletproof windows to compact disks (CDs). The main advantage of this material over other types of plastic is its great strength combined with light weight. While acrylic is 17% stronger than glass, polycarbonate is nearly unbreakable. Bulletproof windows and enclosures as seen inside banks or at drive-throughs are often made of this plastic. Add to this the advantage that it is just 1/3 the weight of acrylic, or 1/6 as heavy as glass, and the only drawback is that it is more expensive than either.
Compact disks and digital versatile discs (DVDs) are perhaps the most readily recognized examples of polycarbonate. Anyone who has archived files on a writable CD, then later tried to break it before throwing it away, knows just how tough this material can be.
Clear polycarbonate is used to make eyeglasses because of its excellent transparency, durability, and high refractive index. This means that it bends light to a far greater degree than glass or other plastics of equal thickness. Since prescription lenses bend light to correct vision, polycarbonate lenses can be thinner than glass or conventional plastic, making it the ideal material for heavy prescriptions. These thin lenses correct poor vision without distorting the face or the size of the eyes, yet this extremely thin lens is virtual indestructible, an important safety factor for children and active adults.
Polycarbonate lenses are also used in quality sunglasses that incorporate filters to block ultra-violet (UV) rays and near-UV rays. The lenses can also be polarized to block glare, and their high impact resistance makes them perfect for sports. Many sunglasses manufacturers choose this material because it can be easily shaped without problems like cracking or splitting, resulting in extremely lightweight, distortion-free, fashionable glasses that feature all of the health benefits doctors recommend.
The electronics industry also uses polycarbonate. It has been used to create transparent colored computer cases, for example, and many cell phones, pagers, and laptops also use it in their casings.
Other uses for polycarbonate include greenhouse enclosures, automobile headlights, outdoor fixtures, and medical industry applications, though the list is virtually endless. Somewhat less toxic than polyvinyl chloride (PVC) to produce, this plastic nevertheless requires toxic chemicals in its production phase. It is, however, recyclable and environmentally preferable to PVC in applications for which either material can be used.
