SEARCH FOR THE SOURCES OF COLOR IN THERMALLY AGED, WEATHERED AND GAMMA-RAY IRRADIATED BISPHENOL-A POLYCARBONATE

Bisphenol A polycarbonate (BPA-PC) is an important high performance en gineering thermoplastic well known for its outstanding combination of toughness, transparency and heat resistance. These properties make it an ideal material for demanding applications where it is exposed to ex ternal stresses such as elevated temperatures, ultraviolet light and g amma-ray sterilization. However, on extended exposure to these conditi ons, BPA-PC slowly degrades, turning progressively more yellow, eventu ally leading to a decrease in its physical properties. Over the years, there has been numerous studies made to understand these degradative processes so as to better design more stable BPA-PC formulations. In t his paper, this chemistry is briefly reviewed along with more recent w ork in this area with a special emphasis on the efforts made to identi fying the actual chemical species responsible for the observed yellow color. and the chemistry responsible for their formation.