Lifetime prediction of food and beverage packaging wastes

Two different types of commercial polyethylene terephthalate (PET) and polypropylene (PP) samples used for beverage and food packaging were degraded for 25 months in isothermal oxidative condition at relatively low temperature (423 K). The results of this long-term experiment were compared with thermooxidative degradations of the same polymers that were carried out in a thermogravimetric (TG) analyzer, at higher temperatures (443 a parts per thousand currency sign T a parts per thousand currency sign 623 K), in isothermal heating conditions. The obtained set of experimental TG data was used to determine the apparent activation energy (E (a)) of degradation through two isothermal kinetic methods with the aim to verify the validity of lifetime predictions of polymers made by degradation experiments at higher temperatures. The results that were discussed and interpreted suggest caution in the extrapolation at lower temperature of degradation kinetics parameters obtained at high temperatures.