Chemiluminescence as an industrial test method for antioxidant effectiveness in polyolefins - 1. Fundamental considerations

Chemiluminescence is an effective tool in the industrial environment, reproducing oven aging results with better accuracy in less time due to the possibility of working with lower antioxidant concentrations and thinner samples under oxygen atmosphere at elevated temperatures. Furthermore the technique allows the characterization of samples with unusual geometry such as powder particles and fibres. Despite its accuracy the impact of geometrical parameters of individual polymer samples must be considered since temperature gradients are observed depending on the sample thickness and arrangement. By means of the method of finite fields, the temperature variation on sample form and thickness can be evaluated. Focusing on polypropylene, even single powder particles and individual fibres can be measured in special sample cavities. This setup reduces the usually observed variation in chemiluminescence induction time. Besides geometrical factors molecular sizes and the chemical nature of antioxidants influence the chemiluminescence induction time: low mobility stabilizers such as oligomeric sterically hindered amines cause no or minor variation of the chemiluminescence induction time in contrast to stabilizers with low molecular weight and high mobility. (C) 1998 Elsevier Science Limited. All rights reserved.