1070-4272/02/7504-0645 $27.00 C 2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 4, 2002, pp. 645!648. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 4, 2002,
Original Russian Text Copyright + 2002 by Bochek, Yusupova, Zabivalova, Petropavlovskii.
AND POLYMERIC MATERIALS
Rheological Properties of Aqueous H-Carboxymethyl Cellulose
Solutions with Various Additives
A. M. Bochek, L. D. Yusupova, N. M. Zabivalova, and G. A. Petropavlovskii
Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
Received June 1, 2001
Abstract-Rheological properties of moderately concentrated aqueous solutions of carboxymethyl cellulose
in the H form with various additives were studied.
It is known that carboxymethyl cellulose sodium
salt (NaCMC) is readily soluble in water at a degree
of substitution (DS) above 0.4. Aqueous solutions
of NaCMC are used in food, cosmetic, fragrance, and
textile industries, in petroleum production, and also
in manufacture of detergents . Heavy metal (Ag,
Pb, Zr, Cu) salts precipitate NaCMC from solutions
. Introduction of Cr(III) into an NaCMC solution
may result in the formation of a gel, in which syner-
esis proceeds in the couse of time . With increasing
Cr(III) concentration, the solution viscosity grows and
The viscosity and structural organization of CMC
solutions depend on the degree of its neutralization
[1, 4, 5]. On passing from the Na to H form (HCMC),
the solution viscosity increases and cross-linking oc-
curs. Dry HCMC is insoluble in water, and its aque-
ous solutions can be prepared by passing NaCMC
solutions through strongly acidic cation-exchange res-
ins . When an HCMS solution free from granules
of a cation-exchange resin is allowed to stand at 53
10oC, gelation starts, caused by accumulation of
weakly dissociated carboxy groups in the polymer
macromolecules [1, 4]. The resulting HCMS gel is
stable in time. We observed no syneresis or polymer
degradation even after keeping an HCMC solution for
a year at 5310oC in an oxygen-free atmosphere .
Thus, a gel obtained from aqueous HCMC is a three-
dimensional (3D) cross-linked system formed through
intra- and intermolecular hydrogen bonding between
the carboxy and hydroxy groups of HCMC and water
Addition of heavy metal salts to HCMC solutions
initiates chemical cross-linking through carboxy groups
of the polymer. It was of considerable scientific and
practical interest to study the effect of various addi-
tives (heavy metal salts and weak bases and acids)
on the rheological properties of aqueous HCMC solu-
tions and also to elucidate the mechanisms of action
of these additives on gelation.
Therefore, we studied in this work the features
of gelation in aqueous HCMC solutions with various
As a starting material we used commercial NaCMC
(degree of substitution DS 0.46; degree of poly-
460). The degree of polymerization
was determined viscometrically using an NaCMC so-
lution in 6% NaOH. We used in calculations the re-
lationship [h] = 7.3 0 10
. The degree of
substitution in NaCMC was estimated from the sodi-
um content by Eq. (1).
= %%%%%%% ,
2300 3 80n
where n is the Na content in the polymer (wt %).
The sodium content in CMC was determined by
conductometric titration with 0.1 N HCl. The degree
of substitution of HCMC by carboxy groups DS
was estimated by Eq. (2).
= %%%%%%% ,
4500 3 58m
where m is the carboxy group content (wt %).
The carboxy group content was determined by con-
ductometric titration with 0.1 N NaOH. The DS
were coincident in the CMC samples studied.