A new method for assessing the efficiency of stabilizers in polyolefins exposed to chlorinated water media

The chlorine used as disinfectant in tap water degrades most materials, including polyethylene. The most adequate (functional) test method, the pressure test, is complicated and expensive because the chlorinated aqueous media (Cl 2 or ClO 2 in water) are unstable and they undergo reactions that are dependent on the pH. A new method which assesses the protection efficiency of phenolic antioxidants in polyolefins was developed. The method uses a liquid hydrocarbon analogue, squalane, in which antioxidants are dissolved. The organic phase was dispersed in the aqueous chlorinated phase (containing 10 ppm of either Cl 2 or ClO 2; pH = 6.8) at 70 °C by intense stirring. The depletion of antioxidant (Irganox 1010) was monitored by standard DSC determination of the oxidation induction time. It was shown that 300 min of exposure was sufficient to obtain useful data.