Synergistic stabilizer systems for the protection of polypropylene from thermal oxidation

Abstract

The antioxidative behavior of 2,2′‐bis(4‐methyl‐6‐tert‐butylphenols) in polypropylene were investigated with and without dilauryl‐thio‐dipropionate. The experimental methods used in this study were thermogravimetric analysis for determining sample weight loss and differential thermoanalysis for obtaining information on oxidative processes and induction periods. The best antioxidant found was the dithio group bridged compound. The methylene‐, n‐butylidene‐, cyclohexylidene‐, and thio‐bridged systems were less active antioxidants. All compounds showed synergism with DLTP. The effectiveness of the synergistic mixtures decrease with decreasing activity of the bisphenol compounds. The pure dithio‐bridged compound was a better antioxidant in polypropylene than is its “synergistic” mixture with DLTP.