Improving Heat Ageing, Mechanical Properties, and Thermal Conductivity of Silicon Rubber by Surface Modification of Iron Oxide and Field Testing of Silicon Rubber O-rings

Abstract

Silicone rubber (SR) compounds were prepared to apply O-ring at high temperatures. Silane surface modified Fe2O3 and unmodified Fe2O3 were added to the SR compounds, and the compounds were assessed by analyses of FESEM (Field-Emission Scanning Electron Microscopy) (for morphology) and TGA and tests of thermal conductivity at different temperatures, thermal aging, hardness, tensile and compression set. Moreover, O-rings were prepared and field tested in an online Gas Chromatograph (GC) of Chemical Analysis in one Petrochemical Company under the pressure of 7 bar and temperature of 180 °C. The obtained results show that the thermal conductivity, aging resistance, thermal stability, and mechanical properties of SR decreased in the following order: surface-modified Fe2O3-filled SR, unmodified Fe2O3-filled SR, and SR without Fe2O3. Overuse of Fe2O3 reduced mechanical properties and hardened processability. The thermal conductivity of SR filled with varying volume percent of modified and unmodified Fe2O3 decreased as the temperature increased. Using surface-modified Fe2O3 increased thermal conductivity and improved aging resistance, ultimately enhancing thermal resistance. It is particularly beneficial for the production of O-rings resistant to high temperatures. The field-test results confirmed that the O-rings were compatible with high-temperature conditions. Furthermore, after testing, the O-rings exhibited low volume swelling and a smooth surface without any cracks, blisters, or unevenness.