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The lifetime of polymers is affected by the consumption and physical loss of the additives used for the improvement of performance. The practice and scientific experiments revealed direct relationships between the service life of the polymer and the transport characteristics of the antioxidants applied. From an effective stabilizer low volatility, high solubility and low diffusion rate are expected. While the first parameter is determined only by the chemical nature of the additive, the solubility and the mobility depends also on the chemical and physical structure of the polymer. In our laboratories the solubility and the diffusion rate of different additives have been studied in amorphous and semicrystalline (ethylene) polymers. The effect of the nature of the small molecules, like size, shape, and hydrogen bonding, as well as the thermal history of the polymer were investigated. Quantitative relationships were established …