Evaluation of effects of thymolphthalein on thermooxidative stability of polypropylene

The present work is aimed to find a new and efficient type of antioxidants for polypropylene. Hence, effects of 3,3-bis(4-hydroxy-2-methyl-5-propan-2-ylphenyl)-2-benzofuran-1-one, generally known as thymolphthalein, on thermo-oxidative stability of polypropylene in solid and melt states were evaluated and compared with those of SONGNOX 1010, an efficient commercially used antioxidant for the polymer. Oven ageing experiments followed by Fourier transform infrared (FTIR) spectroscopy showed that thymolphthalein increased thermo-oxidative stability of the polymer outstandingly in the solid state and its stabilization efficiency was comparable to that of SONGNOX 1010. In addition, measurements of oxidative induction time (OIT) and oxidation onset temperature (OOT) revealed that thymolphthalein improved thermo-oxidative stability of the polymer in the melt state significantly. It was also observed that thymolphthalein did not interfere with the stabilization action of SONGNOX 1010 in the polymer neither in melt nor in solid state. On the basis of the obtained results, a probable mechanism for the stabilization action of thymolphthalein in the polymer is proposed.