Enhanced thermal oxidative stability of silicone rubber by using cerium-ferric complex oxide as thermal oxidative stabilizer

Abstract

AbstractCerium (Ce)-ferric (Fe) complex oxides were prepared via a citric acid sol-gel process, and used as thermal oxidative stabilizers for silicone rubber (SR). The oxides were characterized by X-ray diffraction and Raman spectroscopy. The Ce/Fe molar ratio in Ce-Fe complex oxides significantly influenced the thermal oxidative stability of SR. After aging at 300°C for 24 h, SR filled with 4 phr Ce-Fe complex oxide with a Ce/(Ce+Fe) molar ratio of 0.8 (CeFeO-0.8) exhibited excellent thermal oxidative stability, retaining 56.8% and 54.3% of its original tensile strength and elongation at break, respectively. Some Ce3+ and Fe2+ ions were detected in aged SR composites. Ce3+/Ce4+ and Fe2+/Fe3+ molar ratios in SR/CeFeO-0.8 were less than that in SR/CeO2 and SR/Fe2O3 composites, respectively, as detected by X-ray photoelectron spectroscopy. It implies rapid re-oxidations of Fe2+ and Ce3+ occurred in SR/CeFeO-0.8, enhancing the capacity of CeFeO-0.8 to capture radicals during thermal aging.