CC BY
10
ISSN 1998-4812
BecTHHK EamKHpcKoro yHHBepcHTeTa. 2016. T. 21. №2
331
UDC 541.64:536
C o m m u n i c a t i o n
THE PECULIARITIES OF DYNAMIC BEHAVIOR OF SODIUM SALT CARBOXYMETHYLCELLULOSE IN WATER SOLUTIONS
© V. V. Chernova*, S. R. Miniakhmetova, A. S. Shurshina, D. Sh. Yuzlikbaeva, E. I. Kulish
Bashkir State University Russia, Republic of Bashkortostan, Ufa, st. Zaki Validi, 32
*Email: [email protected]
The dynamic characteristics of the solutions of sodium salt carboxymethylcellulose have been studied and it has been demonstrated that at low shear rates the attainment of crossover point is not accompanied by the formation of catching network. The shear rate increase results in the fact that catching network is formed practically simultaneously with attaining crossover point.
Keywords: chitosan, viscosity, dynamic characteristics, catching network.
Introduction
It is known that in diluted polymer solutions with the concentration C lower than the so-called crossover concentration C* (the concentration of the beginning of macromolecules overlapping) macromolecules flow irrespectively of each other while at C>C* (in a semi-diluted solution) the macromolecules motion is retarded because of their mutual influence. This is accompanied by the formation of catching network at polymer concentration in the solution Ce. In solutions of non-iono-genic polymers C*~Ce. However, in solutions of iono-genic polymers the likely charged units of macromole-cules repell each other, which inhibits the formation of eatching network, resulting in C*^Ce. Previously such peculiarities of dynamic behavior of ionogenic polymer solutions have been demonstrated by chloride polydime-thyldiallilammonia [1], polyacrylic acid [2], chitosan and chitosan succinamide [3]. In the given study the dynamic behavior of ionogenic polymer - sodium salt carboxymethylcellulose (CMC) has been investigated.
Experimental part
CMC produced by the company «Vekton», Russia was used as the object of investigation. The intrinsic viscosity was determined by means of viscosimeter Ub-belohde at the temperature of T=25±1C. The value of intrinsic viscosity of the sample under investigation in bidistilled water was 30.1 dl/g. Rheological dynamic flow meter Haarke Mars III at T=25±1C under the operating conditions of continual shear deformation in the range of shear rates from 0.1 to 100 c-1. The viscosity determined at the shear rate equal to 0.1 c-1 was taken for the highest Newtonian viscosity, that at the shear rate of 100 c — for the lowest one.
Results and discussion
Curve 1 shows the dependence of the highest Newtonian viscosity q on the polymer concentration in the solution in double logarithmic coordinates. The formation of catching network with corresponding viscosity increase in seen to occur at the concentration Ce~0.3 g/dl. However, taking into consideration that the value of crossover concentration is equal to C*=1/[q] ~ 0.030 g/dl it should be admitted that the attainment of C* doesn't affect the mechanism of polymers flow. In this connection in the case of CMC solutions one can speak about the presence of a transition area in which macro-molecules come into contact with each other but the catching network isn't formed yet. It is interesting that if for constructing lgq-lgc plot not the highest values of Newtonian viscosity but the lowest ones are used the situation changes. Curve 2 shows that in fact immediately
after the transition of diluted solution into semi-diluted one there starts the formation of catching network and in this case C*~Ce. It is evident that the increase in shear rate at rheological experiments results in overcoming the forces of electrostatical repelling between macromole-cules, due to which the catching network starts to be formed immediately after attaining the crossover point.
Fig. The dependence of the highest ( 1 ) and lowest (2) Newtonian viscosity in water solutions of sodium salt carboxymethylcellulose on its concentration in the solution.
REFERENCES
1. Litmanovich E. A., Orleneva A. P., Korolev B. A., Kasaikin V. A., Kulichikhin V. G. Dynamics of polymer chain in aqueous and salt-containing aqueous solutions of poly (dimethyl dial-lylammonium chloride) // Polymer Science, Ser. A. 2000. V. 42. №6. P. 1035-1041.
2. Dreval' V. E., Vasil'ev G. B., Litmanovich E. A., Kulichikhin V. G. Rheological properties of concentrated aqueous solutions of anionic and cationic polyelectrolyte mixtures // Polymer Science, Ser. A. 2008. V. 50. №7. P. 751-756.
3. Bazunova M. V., Valiev D. R., Chernova V. V., Kulish E. I. Rheological properties of solutions of chitosan and its complexes with colloid particles of a silver iodide sol// Polymer Science, Ser. A. 2015. V. 57. №5. P. 675-679.
Received 19.05.2016.
