Kinetic Evaluation of Reactivity of Phenolic Derivatives as Antioxidants for Polypropylene

Reactivity of commercial phenols as antioxidants for plastics, especially polypropylene, was examined under kinetic considerations. Inhibitive rate constants, kinh, were found to decrease in the order: SWP ≳ Topanol CA ≫ BMP > Ionox 330 > Irganox 1076 > Irganox 1010, while numbers n′ of free radicals trapped by the phenolic moiety decreased in the order: Irganox 1076 > Irganox 1010 ≳ Ionox 330 > BMP ≫ Topanol CA > SWP (the structures of these antioxidants are given in the text). In practical use of phenols for polypropylene, it was found that effective phenols are not those having higher values of of kinh., but n′ values nearly two. The effect of substituents, especially para substituents, of phenols on their activities was elucidated.