SORPTION AND RHEOLOGICAL PROPERTIES OF LOW-CONCENTRATED CROSS-LINKED SOLUTIONS OF SODIUM SALT OF CARBOXYMETHYLCELLULOSE

The sorption and rheological properties of low-concentration Na-CMC solutions cross-linked with aluminum ions and complex compounds of aluminum with citric acid were studied. It was found that when the pH value of the structured system increases from 2.4 to 4.9, the dynamic viscosity increases. It has been shown that with increasing concentration of the initial Na-CMC, the effective viscosity increases. With an increase in the number of chemical cross-links and concentration in the system, higher values of effective viscosity and shear stress of Na-CMC hydrogels are observed, which is due to an increase in the structure of the system. The sorption capacity of dried gels was studied and it was shown that with an increase in the size of the cross-linking agent using citric acid, the pore radius of the cross-linked system increases significantly, which promotes cross-linking of sections of one or different chains that are more distant from each other in space with the same initial conformation of the cellulose chain. The likelihood of intermacromolecular cross-linking responsible for gelation increases with increasing initial concentration and with the additional presence of polybasic acids. When the pH value of the medium changes, the cellulose chain of the Na-CMC macromolecule in solution takes on a different conformation. Depending on the initial conformational state of the cellulose chain and the length of the cross-linking agent, Na-CMC gels with different structures can be obtained.