Oxidative and Thermal Stability of Antioxidants Extracted from Palm-Pressed Fibre in Base Oil

The lower oxidative stability of lubricating oil can be mitigated or retarded by scavenging free radicals from phenolic compounds, an additive usually derived from plants due to their lower toxicity. The phenolic compounds have an antioxidant effect that donates an atom to stop the oxidation process in the reaction chain. In this work, the thermal and oxidative stability of natural antioxidants extracted from pressed palm fibres was investigated. The antioxidant compounds were extracted by ultrasound-assisted extraction with 70% ethanol at 30 min and a ratio of 1:40 (sample to solvent). The antioxidant was added to different types of mineral oil before its functional groups were investigated by Fourier transform infrared spectroscopy (FTIR) and its thermal and oxidative stability by the thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC), respectively. The results showed that the antioxidants changed the functional groups in the mineral oil and the base oil and increased the thermal stability of the base oil by about 20 °C. The thermal stability in the DSC also showed an increase in the initial temperature due to the presence of antioxidants from − 79.0 to − 0.4 °C.