ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 4, pp. 660!664. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + I.I. Goncharik, F.F. Mozheiko, T.P. Kulikova, Z.A. Gotto, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 4,
pp. 676 ! 680.
AND POLYMERIC MATERIALS
Stability and Structural and Rheological Properties of Rapeseed
Oil-Based Emulsions in the Presence of Sodium Carboxylates
I. I. Goncharik, F. F. Mozheiko, T. P. Kulikova, and Z. A. Gotto
Institute of General and Inorganic Chemistry, National Academy of Sciences of Belarus, Minsk, Belarus
Redceived July 11, 2006; in final form, January 18, 2007
Abstract-Formation conditions and structural and rheological properties of rapeseed oil-based emulsions
in the presence of sodium laurate and sodium palmitate were examined.
Formation of emulsions requires introduction into
the water3oil system of an emulsifier to promote crea-
tion of a strong adsorption layer at the interface and
to increase their stability. As oil phase can serve vege-
table oils (linseed, hempseed, sunflower, rapeseed,
etc.). In recent years, especially wide application has
been enjoyed by rapeseed oil and emulsions thereof.
We have elucidated previously  how the stability
and structural and rheological properties of rapeseed
oil-based emulsions is influenced by inorganic electro-
lytes. To prepare stable emulsions, emulsifiers (various
surfactants) are typically introduced into the emulsion.
The most widely used for these purposes are sodium
carboxylates (soaps). Therefore, it was of interest to
examine how the stability and structural and rheolog-
ical properties of rapeseed oil-based emulsions are
influenced by soaps. The increased interest in soaps is
also due to the fact that they are components of wastes
in many chemical productions. For example, adipates
are alkaline waste from caprolactam production, and
spent lye, the waste from soap manufacture; they can
also serve as emulsifiers in preparation of emulsions.
As is known , only high-molecular-weight soaps
(alkaline salts of lauric and fatty acids with higher
molecular weights) are used as emulsifiers.
In this study, we used as emulsifiers chemically
pure-grade sodium laurate and sodium palmitate, as
well as rapeseed oil produced according to GOST
(State Standard) 8988377.
Emulsions were prepared by the procedure from
. After 15-min dispersing, a portion of the result-
ing emulsion was placed in calibrated test tubes, and
the phase separation in the systems of interest was
monitored visually. As the measure of stability we
took the percentage ratio of the volume of the sep-
arated aqueous or oil phase to that of the entire ini-
tially prepared emulsion. The remaining emulsion
was used for examining the structural and rheological
properties and electrical conductivity. The structural
and rheological examinations were carried out on
a Rheotest 2 rotary viscometer in the coaxial-cylinder
system at the strain rate within 3.031312 s
on the measured data, we calculated, for each velocity
gradient D, by standard procedures  the shear stress
and the effective viscosity h. The examination of
the equilibrium shear stress in relation to the strain
rate yielded full rheological curves.
We found that the stability of the emulsions de-
pends on the concentration of the oil phase and emul-
sifiers, as well as on the nature of the latter. The re-
sults are presented in Table 1. It is seen that sodium
laurate stabilizes only the water3rapeseed oil system
containing 75% oil phase. The stabilizing effect of
sodium laurate is manifested even at low concentra-
tions. For example, upon introduction of 0.4 0 10
and 0.8 0 10
M of the emulsifier, 36 and 40%, re-
spectively, of the oil phase separates within 1 day from
the resulting emulsion, whereas without the emulsi-
fier, the emulsion completely separates within this
time into the oil and aqueous phases. Upon increasing
the sodium laurate concentration to (8.0356)0 10
the emulsion preserves stability even for 10 days.
Evidently, at these concentrations, the adsorption
layer formation at the liquid3liquid interface is com-
plete, which ensures high stability of the emulsions.
Introduction of sodium laurate into the system con-
taining 25, 50, and 90% oil phase leaves the emulsion
stability virtually unaffected.