Chemistry Reference
In-Depth Information
Figure 11.4 TGA thermograms of ESBO, the 20% hexanoic anhydride (HA) in ESBO,
crude Hex-SBO, Hex-SBO and HA obtained from the Kugelrohr distil-
lation of crude Hex-SBO, showing weight (%) loss with temperature.
(Reproduced from ref. 47 with kind permission from Springer Science
and Business Media from Springer and the AOCS Press.)
crude Hex-SBO, and HA obtained from the Kugelrohr distillation of crude
Hex-SBO and the final diester product Hex-SBO. The percentages of an-
hydride obtained using the TGA method for the final diester products were
Ace-SBO 2%; Isobut-SBO 1.9%; But-SBO 1.7%; and Hex-SBO 2%.
Similarly, FT-IR was used to monitor the removal of unreacted anhydride.
The peak for the anhydride carbonyl group appears at 1818 cm
1
and is
easily distinguishable from the ester carbonyl peak at 1743 cm
1
.In
Figure 11.1, a peak at 1818 cm
1
can be seen in a crude Hex-SBO. Complete
removal of unreacted anhydrides using Kugelrohr distillation of the final
diester products (Ace-SBO, But-SBO, and Isobut-SBO) was confirmed by the
absence of the 1818 cm
1
peak in their spectra (Figure 11.1).
11.3.3 Oxidation and Thermal Stability
The TGA profiles show that the diesters are as thermally stable as ESBO, even
at high temperatures (Figure 11.4). Noack volatilities were also determined
as per the ASTM D6375 method using TGA and are shown in Table 11.3.
Noack volatilities for all the samples were less than 3%, which are excellent
compared to the 10-30% for mineral oils and synthetic esters. These diester
derivatives are therefore thermally stable. PDSC (pressure differential scan-
ning calorimetry) experiments were used to measure the oxidation stability
of CMSBO samples. This test is widely used in the lubricant industry and
