Hot air aging behavior of polypropylene random copolymers

This article deals with the global aging behavior of three polypropylene random copolymer (PPR) materials with varying primary structure and morphology. Hot air aging experiments at elevated temperatures from 95 to 135C were carried out using microsized specimens with a thickness of 100m. Technological and analytical aging indicators were monitored for an exposure time of up to 750days. Independent of comonomer type (ethylene vs. butylene) and morphology ( vs. crystal form) a critical molar mass of 300kgmol1 was obtained. The consumption of antioxidants was slower for the nucleated PPR grade with finer spherulitic structure. The grade outperformed the crystal PPR grades resulting in about 20% higher timetoembrittlement values.(VLID)356326