Bio-Lubricants Development: The Potential Use of Boron-Containing Additives

Abstract

This paper reports the use of boron-containing additives to improve the performance of a bio-based lubricating oil. The base oil was prepared from glycerol and oleic acid, was fortified with antifoaming agent, phenyl-α-naphtylamine, 4,4’-methylene-bis(2,6-ditert-butyl) phenol, and benzotriazol and has met the SAE 90 gear oil viscosity classification. The additives was prepared by reacting boric acid with monoethanolamine and was used in all formulations at 0.01 %wt of boron/kg. The test of extreme pressure property was carried out to examine the load-carrying capacity of the lubricating fluids using the four-ball extreme pressure tester according to ASTM D-2783. The oxidation & corrosion test was carried out using the bulk test at 150oC for 24 h. Steel & copper specimens weight losses were used to estimate the lubricants corrosiveness. Meanwhile, kinematic viscosity increase at 40oC was used to measure the effect of formulation to the oxidation stability of the oil. Experimental results showed that when used alone, the boron-containing additive exhibited antioxidant activity, i.e. prevention of viscosity increases, and protection against corrosions, particularly to copper. The formulation did not show any noticeable effects on extreme pressure characteristics. Nevertheless, when used in combinations with dibutyl phosphite and/or 2,5-dimercapto-1,3,4-thiadiazol, significant improvements in load – wear indices were shown. The best achievement reached a last non-seizure load of 40 kg, a weld point of 400 kg, and a load – wear index of 54.37 – 55.47. The antioxidant activities were decreased when boron was used in combinations with these additives even though their oxidation stabilities were better than that of the base case oil. The combination with 2,5-dimercapto-1,3,4-thiadiazol also showed a better rust/corrosion prevention.