Chemistry Reference
In-Depth Information
approximately 2 h, the catalyst containing the oxidized oil was weighed to
determine the volatile loss (or gain) due to oxidation and then soaked
(30 min) in THF to dissolve the soluble portion of the oxidized oil. After
dissolving the soluble portion of the oxidized oil, the catalyst was dried and
weighed to determine the remaining insoluble deposit.
11.2.4.2 Pressurized Differential Scanning Calorimetry
The experiments were carried out using a PC-controlled DSC 2910 thermal
analyzer from TA Instruments (New Castle, DE). The instrument has a
maximum sensitivity of 5 mV cm
1
and a temperature sensitivity of
0.2 mV cm
1
. A 1.5-2.0 mg sample was placed in a hermetically sealed type
aluminum pan with a pinhole lid for interaction of the sample with the
reactant gas (dry air). The controlled diffusion of the gas through the hole
greatly restricts the volatilization of the oil while still allowing for saturation
of the liquid phase with air. A film thickness of less than 1 mm was required
to ensure proper oil-air interaction and to eliminate any discrepancy in the
result due to gas diffusion limitations. The module was first temperature
calibrated using the melting point of indiummetal (156.6 1C) at a 10 1Cmin
1
heating rate. Dry air was pressurized in the module at a constant pressure of
3450 kPa and a scanning rate of 10 1Cmin
1
was used throughout the
experiment. The signal maximum (SM) and onset (T
onset
) temperatures were
calculated from the exotherm in each case. The induction time (I
t
) was
measured for oils containing different additive (phenolic anti-oxidant)
concentrations (0.5-2.0 wt%) using an isothermal scanning rate.
11.2.4.3 Friction Measurement by the Ball-on-disk Method
The boundary lubrication properties of SBO, HOSBO and ESBO were studied
using a multispecimen friction measurement apparatus (FALEX, Sugar
Grove, IL). Ball-on-disk experiments (1018 steel disk, R
c
15-25) were carried
out under low speed, 6.22 mm s
1
(5 rpm), and high load 181.44 kg at 25 1C
using test oils diluted to different concentrations with hexadecane. Meas-
urements of the coecient of friction (COF) and torque were made in each
case. The COF values reported are averages of two or three independent
experiments and the standard deviation observed was
0.02.
11.3 Results and Discussion
11.3.1 Physical Properties of the Vegetable Oils Investigated
The physicochemical properties of SBO, HOSBO, ESBO and moringa oil are
presented in Table 11.1. The viscosity of ESBO at 40 1C is significantly larger
than the other oils. The higher molecular weight and more polar structure
compared with SBO and HOSBO results in stronger intermolecular inter-
actions in ESBO. This property of ESBO would translate into enhanced lubricity
