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].