Chemiluminescence - a useful technique for characterizing the stability and forecasting the lifetime of polymer materials for nuclear applications

The chemiluminescence (CL) mechanism is tightly related to the polymer oxidation mechanism both of them proceeding by means of peroxidic species (free radicals) and hydroperoxides of the polymer. The CL emission is strongly influenced by the stabilizing antioxidants, the efficiency and concentration of which being correlated with the CL signal.. This paper presents the mechanism of CL emission, the methods of materials characterization of polymers based on polyethylene and additives, evaluation of the materials lifetime as well as recent experimental examples regarding the characterization of the efficiency of some stabilizing agents (antirad agents of the type of radical captors or energy deactivators). Also the study of some synergic effects, and the diagnosis of degradation of some cable isolations exposed to electrical or radiation fields. The results obtained were correlated with those obtained by other techniques, namely, IR, UV spectroscopy, thermal analysis, electrical tests, oxygen absorption, chemical and mechanical tests, which demonstrated the high sensitivity of the method. Since the CL tests need only small material amounts, of the order of 2-4 mg, the method can be used for characterization of raw materials and products of fabrication as well as in the diagnosing the degradation of samples exposed to service-like conditions to evaluate the lifetime expectation or the remaining service time