1070-4272/05/7808-1329 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 8, 2005, pp. 1329!1332. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 8, 2005,
Original Russian Text Copyright + 2005 by Sultanova, Rakhmatullina, Akhmed’yanova, Liakumovich.
AND POLYMERIC MATERIALS
Emulsion Polymerization of Styrene in the Presence
of a Mixture of Potassium Stearate and Oleate
G. I. Sultanova, A. P. Rakhmatullina, R. A. Akhmed’yanova, and A. G. Liakumovich
Kazan State Technological University, Kazan, Tatarstan, Russia
Received April 21, 2005
Abstract-The features of emulsion polymerization of styrene in the presence of a mixture of potassium
stearate and oleate was studied. The effect of these salts on the polymerization rate and the yield and molec-
ular weight of polystyrene was examined.
Making the existing processes for latex production
more feasible and efficient remains a topical prob-
lem. This goal can be accomplished, in particular,
by choosing effective emulsifiers that could provide
a high conversion of the monomers and aggregative
stability of the latexes.
It is known that effective emulsifying systems for
synthesis of diene3styrene and styrene3acrylate dis-
persions contain mixtures of different types of sur-
factants . At the same time, impurities of potas-
sium myristate, palmitate, stearate, or linoleate in
the commercially used emulsifier, potassium oleate,
decrease the polymerization rate and mechanical sta-
bility of butadiene3styrene latex .
We found previously that a 40 : 60 (by weight)
mixture of stearic and oleic acids exhibits synergism
in its effect on some properties of rubber stocks and
vulcanizates . This fact suggests that these sur-
factants may affect nonadditively the preparation and
properties of other polymers.
As a model for examining the effect of a mixture of
stearic and oleic acids in the form of potassium salts
on the emulsion polymerization, we chose polymeri-
zation of styrene.
The emulsion polymerization was performed at
80oC for 90 min. The composition (wt parts) of the
reaction mixture was as follows: styrene 100, fatty
acid 1.2, KOH 0.18, K
0.5, and water 160.
The reaction progress was monitored gravimetrically.
Samples were taken at definite intervals and analyzed
to determine the polymer yield (%) by the formula 
N = P
is the polymer weight in the sample (g), and
is the monomer weight in the sample (g), calcu-
lated from the initial monomer concentration.
The viscosity-average molecular weight of the iso-
lated polystyrene was determined by the procedure
described previously .
The surface tension of aqueous solutions of potas-
sium soaps of fatty acids was determined by the Du
Nouy method . The limiting adsorption G
termined graphically from the adsorption isotherms
of the surfactants [9, 10]. The negative logarithm of
the surfactant concentration at which s decreases by
20 mN m
) was determined by a procedure
described in , and the critical micellization con-
centration (CMC), according to [12, 13].
Figures 1a31c show that the polymerization kinet-
ics depends on the emulsifier composition, namely,
on the ratio of stearic (St) and oleic (Ol) acids in
the potassium salts [K(St : Ol)]. The styrene conver-
sion as a function of the emulsifier composition passes
through a maximum at the K(St : Ol) ratio ranging
from 40 : 60 to 60 : 40 wt %, with the polystyrene
yield (Fig. 2, curve 1) equal to 99.9%.
The viscosity-average molecular weight (M
polystyrene as a function of the K(St : Ol) ratio also
passes through a maximum, 460000, observed at
K(St : Ol) = 40 : 60 wt % (Fig. 2, curve 2).
The dependences of the mean reaction rate (W
on the styrene conversion (Fig. 3) are, on the whole,
similar at different emulsifier compositions, with
the highest W
attained at 60% conversion. However,