Tribological Analysis of Modified RBD Palm Kernel Containing Anti-oxidant Additive using Four-ball Tribotester
Keywords:RBD palm kernel, ASTM D4172, four-ball tribo-tester, vegetable oil, lubricant oil
Vegetable oils are becoming increasingly important as an alternative lubricant oil due to their non-toxic, renewability and biodegradability characteristics. They are considered as promising candidate to replace the conventional petroleum based lubricant which are constantly threatening our environment. However, most of the vegetable oils are facing common issue which is low oxidative stability that limits them to be used directly as bio-lubricant oil. This work studied the application of TertiaryButyl-Hydroquinone (TBHQ) as synthetic base anti-oxidant agent inside palm kernel oil (PK). The effect of load on the tribological performance of lubricant formulated were tested using four-ball tribo-tester according to ASTM D4172 standard with duration of 60 minutes for each test. The results obtained were compared to the commercialized mineral (MO) and semi-synthetic engine oil (SSO) for the reference purpose. Based on the result obtained, the coefficient of friction of palm kernel is smaller as compared to commercialized petroleum based oil. This is contributed by the presence of long polar fatty acid structure that acts as a protective film between two rubbing surfaces. The addition of anti-oxidant, TBHQ also helps to further reduce the friction coefficient of PK. However, the wear scar diameter of PK and PK+TBHQ are larger compare to MO and SSO. Thus, it can be concluded that TBHQ manage to enhance the friction reducing performance of PK by lowering the value of friction coefficient. However, there is still room improvement for the anti-wear properties of palm kernel oil.