Effects of Manganese Stearate on Stabilization Efficiency of Phenolic Antioxidants in Polypropylene

The present study was aimed to finding a formulation for an additive to produce oxo-biodegradable films that accelerates oxidative degradation of the films after conservation of properties over a span of certain service life. Thermal oxidation behavior of polypropylene (PP) films (approximately 250 μm thick) containing various weight ratios of a commercially used phenolic antioxidant (SONGNOX 1010) to manganese stearate as pro-oxidant has been studied in both melt and solid states. Thermo-oxidative stability in melt state was studied using differential scanning calorimetry (DSC). The rate of thermal oxidation in solid state was investigated via oven ageing experiments at 90 °C followed by measuring changes in FTIR spectra of the film samples. Comparing thermo-oxidative stability of the PP samples containing a combination of SONGNOX 1010 and manganese stearate with the samples containing SONGNOX 1010 alone confirmed that manganese stearate reduces the stabilization efficiency of the antioxidant in the polymer in both melt and solid states. It was also shown that the efficiency of the phenolic antioxidant in thermo-oxidative stabilization of the polymer in both melt and solid states could be changed by altering weight ratio of antioxidant/ pro-oxidant. Finally, it was concluded that the weight ratio of 0.35/0.1 of the antioxidant to the pro-oxidant is suitable for attaining desired stability during melt processing as well as retaining properties during a reasonable service life when is used as a film and a favorable rate of thermal oxidation after the service life.