Measurement of diffusion of antioxidants in isotactic polypropylene by isothermal differential thermal analysis

Abstract The diffusion of the phenolic antioxidant 1,3,5‐tris(3,5‐di tert ‐butyl‐4‐hydroxybenzyl)mesitylene (IRGANOX 1330) in extruded sheets of isotactic polypropylene (iPP) was investigated over the temperature range from 80 to 120°C by isothermal differential thermal analysis (DTA). The measurements showed a clear relation between oxidation induction time and oxidation maximum time (both determined by isothermal DTA) and the concentration of stabilizer. It was possible to calculate the diffusion coefficients and the activation energy of diffusion of IRGANOX 1330 in iPP by measuring the oxidation maximum times across stacks of isotactic polypropylene sheets.