Sodium Carboxymethyl Cellulose(CMC) is a representative cellulose ether, and its sodium salt is used widely in industry. Sodium Carboxymethyl Cellulose(CMC) belongs to anionic polymer electrolyte, besides CMC-Na, it has other salts, such as ammonium and aluminum salt. Sodium Carboxymethyl Cellulose (CMC) sometimes can change to CMC acid. D.S, that is the average of the hydroxyl which reacts with substitute on each anhydrous glucose unit, when D.S is 1:00, its molecular formula is [C6H7O2(OH)2OCH2COONa]n,
Main Properties of Products
Sodium Carboxymethyl Cellulose(CMC) is an odorless, tasteless, non-toxic white powder or micro-yellow fibrous in the pure state.
Sodium Carboxymethyl Cellulose(CMC) is easy to absorb moisture, it dissolves easily in cold or hot water as the colloidal solution, it can not dissolve in many organic solvents such as methanol, ethanol, acetone, chloroform, benzene and so on. The degree of substitution (D.S) is an important factor affects its water-soluble, the viscosity also affects its water-soluble greatly. Sodium Carboxymethyl Cellulose(CMC) is usually alkali when viscosity between 25mPa.s-50000mPa.s, D.S is about 0.3. Sodium Carboxymethyl Cellulose(CMC) is water-soluble when its D.S is more than 0.4. With the increase of D.S, the transparency of the Sodium Carboxymethyl Cellulose(CMC) water substitution becomes much better. Like another macromolecule dielectric, when Sodium Carboxymethyl Cellulose(CMC) dissolving, the first phenomenon is expansion, and then dissolved gradually. So in the preparation solution, the particles should be uniform wetting, then the Sodium Carboxymethyl Cellulose(CMC) can be dissolved quickly. Otherwise, the Sodium Carboxymethyl Cellulose(CMC) is an expansion in water solution, the particles form a strong involucre or plastic coating so that the particles scattered difficulty resulting in dissolution difficulty.
The balance moisture of Sodium Carboxymethyl Cellulose (CMC) with the increase of air humidity increased, with the rise in temperature decreases. At room temperature and the average humidity 80-85%, the balance of moisture more than 26 percent, however the moisture of products less than 10%, lower than the balanced moisture. Even if the moisture content at about 15 percent, there have no difference in appearance. But when moisture content at more than 20 percent, some particles adhere to one another will be able to see, the higher the viscosity, the more obvious of the phenomenon.
The Sodium Carboxymethyl Cellulose(CMC) is a polarity macromolecule compound, its degree of absorbing moisture dominated by the relative humidity, but also the number of polarity group. The higher the D.S, that is, if the number of polarity group is larger, the degree of absorbing moisture is bigger.
1. The viscosity of Sodium Carboxymethyl Cellulose (CMC) water solution is the specific performance of Polymerization Degree of the cellulose, it depends on the average degree of materials cellulose, and the degradation of polymerization degree in the course of basification and etherification reaction, including the reaction uniformity. The viscosity of the Sodium Carboxymethyl Cellulose(CMC) solution with the increase of its concentration and the increasing trend was similar to a straight line. Solution viscosity has a relative with the polymerization degree of the cellulose and its distribution, but also have relative with the solution concentration, pH value, temperature, velocity gradient, D.S and so on.
2. The Effect Factors of Viscosity
Concentration: Regardless of high, medium and low viscosity of the Sodium Carboxymethyl Cellulose(CMC), the viscosity increased with its concentration increase, the logarithm value about concentration and viscosity is approximating beeline.
pH Value: The viscosity of the 1% Sodium Carboxymethyl Cellulose solution is in the largest and most stable state when pH value at 6.5-9.0. Generally, the changes in the viscosity are not very large when the pH at 9.0-11.0. However, PH <6, the viscosity will decline rapidly, and began to form CMC acid, and decline entirely when PH ≌ 2.5; if PH> 9, the viscosity will decline also, at first decline slowly, but when the PH> 11.5, it began a sharp decline. This is because the un-substitution hydroxyls combined with the base molecules, and promote cellulose scattered.
Temperature: The viscosity of the Sodium Carboxymethyl Cellulose(CMC) solution with an increase of temperature. When cooling, the viscosity will rebound, but when the temperature rose to a certain extent, it will be in permanent lower viscosity state. The decline of the viscosity has a closely related to its degree of substitution, the higher the D.S, the viscosity less affected by temperature. Impact of Salt: The existence of all kinds of inorganic salt ions would reduce the viscosity of CMC solution, the effect almost depends on the value of the cation. Generally, it is water-soluble salt when met one value cation, it is water-insoluble salt when met trivalent cation, the water-soluble is between one and trivalent when met bivalent cation.
Impact Velocity Gradient: Because the Sodium Carboxymethyl Cellulose(CMC) solution is non-Newtonian fluid, but belongs to the pseudoplastic fluid. Their mobile properties can not be depicted by a simple Newton's formula, but the apparent viscosity of the solution is still the function of velocity gradient at determining. For a Newtonian fluid, the relationship of its velocity gradient and tangential force is directly proportional.
For pseudoplastic fluid, the increase of the velocity gradient with the increase of tangential force is faster than a straight line, that is to see, the viscosity will reduce with the increase of the tangential force.
For the Sodium Carboxymethyl Cellulose(CMC) solution, its viscosity changes with the velocity gradient can be explained: Because the dispersed phase of Sodium Carboxymethyl Cellulose (CMC) is hydrophilic, after sopping water, at first it will expand, and then dissolved as macromolecules. Because the volume of the molecules is large, the viscosity is great. If the tangential force is increasing, the macromolecules begin directional function, the long axis will be gradually transformed into the flow direction, and the tangential force bigger, the more complete the turning, so the viscosity resistance becoming smaller when the Sodium Carboxymethyl Cellulose (CMC) solution flowing. At the same time, the solvent layer around the Sodium Carboxymethyl Cellulose(CMC) can also be deformed due to tangential force changing, which is the reason for the resistance reducing. In low concentrations Sodium Carboxymethyl Cellulose(CMC) solution, velocity gradient affect on the viscosity is very small, when the solution concentration increases, the velocity gradient affect on viscosity also increases. The viscosity of the Sodium Carboxymethyl Cellulose(CMC) solution will increase with the D.P increasing, but the increase rate of the viscosity is different because of the degree of substitution.
Sodium Carboxymethyl Cellulose(CMC) will deposit when met with heavy metal salts, such as PbSO4, FeCl3, FeSO4, CuSO4, K2Cr2O7, AgNO3, SnCl2, and so on.