Predicting the efficiency of antioxidants in polymers

The efficiency of antioxidants in polymers is determined by three processes: the chemical reactivity, the physical loss and a minimal effective concentration. In most cases, loss of the stabiliser by physical processes (evaporation, leaching) is more significant than the loss by chemical consumption. In this paper, a model is proposed that relates the protection time of an antioxidant to the migration in a polymer matrix. The parameters that determine the migration, i.e. mobility (D) and solubility (S) are predicted using theoretical modelling. A linear correlation was found between the protection time and the function −S ln(D). In some cases this correlation is better than that of the empirical model proposed by Moisan, ln(S2/D).