THE CHEMISTRY OF GAMMA-IRRADIATED BISPHENOL-A POLYCARBONATE

On exposure to sterilizing doses of Co-60 gamma-rays, bisphenol-A poiycarbonate (BPA-PC) turns a moderately intense yellow color. Product studies of gamma-ray irradiated BPA-PC and a model compound, BPA-PC cyclic tetramer, were undertaken to define the major degradative process involved, and to try to identify the chemical species responsible for the color. The major irradiation products were isolated and identified using base hydrolysis followed by HPLC/MS analysis. These studies show that the principal degradative process induced by gamma-ray irradiation involves Fries type free radical reactions leading to the destruction of the carbonate linkages and formation of a number of phenol coupling products and salicylate esters. Chromatographic/spectroscopic studies indicated that the yellow color was mainly due to the formation of two labile products having a broad lambda(max) at similar to 360 nm. However, numerous attempts to isolate and identify these compounds using HPLC/MS and GC/MS were unsuccessful.