Environmental stress cracking resistance of a new copolymer of bisphenol-A

The environmental stress cracking (ESC) behavior of Lexan® SLX (LEXAN is a trademark of General Electric Company) polyester carbonate has been studied. Many factors affect the ESC resistance. Of these, residual stress, orientation, Mw and test time were discussed. Annealing above Tg can effectively eliminate or reduce the effect of residual stress and orientation on ESC resistance, thus allowing true material property rather than effect of processing to be exhibited. The dependence of critical strain on Mw was evaluated. Mw, once above 18,000, showed negligible effect on critical strain provided the test samples were annealed above their Tgs. Thirty eight chemicals covering a wide range of polarity, from non-polar aliphatic hydrocarbons to highly polar formamide and water, were evaluated. The total solubility parameter (Hildebrand solubility parameter) did not correlate with ESCR performance. Hansen solubility parameters were also attempted. A combination of δp-δh and δt-δh plots were found to best describe the severity of environmental stress cracking of a challenging chemical. Lexan® SLX product was generally found to perform much better than bisphenol-A (BPA) PC to ESC. It showed good ESCR performance against aliphatic hydrocarbons, siloxanes, aliphatic alcohols and chemicals of very high polarity and hydrogen bonding interactions such as formamide and water.