3.3.1. Specific Gravities (SG) of synthesized PKO biolubricants
As could be seen in Table 1, the specific gravity value of PKO biolubricant PKBLT synthesized by transesterification with trimethylolpropane (TMP) (0.990 g/mL), is similar to that PKBLE synthesized by epoxidation-esterification (1.10 g/mL). However, it could be seen from the table that there was increase in the specific gravity of these two samples when compared to the SG of the raw PKO sample (0.910 g/mL). However, the petroleum lubricant had the least SG value of 0.848 g/mL. The higher SG values of the PKBLT and PKBLE samples, compared to the PKO value, was attributed to increase in molecular complexity resulting from the trimethylolpropane (TMP) backbone and the elongated chain of the triester, resulting from the epoxy ring opening, respectively [1,40]. It could be seen that the specific gravity value for the biolubricant samples were higher than the petrolubricant. This could be attributed to chemical structural change in the constituent molecules. It is worth noting that the specific gravity change leads to a corresponding change in the mass of the products. In other words, the higher the specific gravity, the heavier and more viscous the lubricant oil would be. Hence, the biolubricant has the advantages of better sustenance at elevated temperature, as well as the ability to withstand greater loads [42]. The compatibility of biolubricant products with either the heavy or light duty engines is determined by its SG. This compatibility is the ability of the sample to mix with other liquids [42]. As such, materials with lower SG (<1) floats in water, where as those with higher SG (>1), sink in water. Therefore, biolubricants with higher SG and viscosity, last longer on the applied surfaces and joints [1,42].