Advantages and limits of hydroperoxide titration methods in solid polymers

Three titration methods developed for the determination of concentrations of hydroperoxides formed in photo-oxidized polymers are reviewed. They are based on the reduction by sodium iodide, by ferrous ion and by gaseous sulfur dioxide. The advantages and the limits of these methods are described on several polymer samples studied recently in the laboratory: the iodide method can be used only when the hydroperoxides are thermally stable up to 80°C. On the other hand, the ferrous ion method is particularly well adapted to unstable hydroperoxides but this method requires the complete solubilisation of the polymer. Lastly, the sulfur dioxide method can be easily carried out, but with some polymers secondary effects are observed which perturb the measurements.