Influencing Factors on Sodium Carboxymethylcellulose Viscosity

An important property of Sodium carboxymethylcellulose is to form the colloidal solution with a certain viscosity when soluble in water. The factors that influence viscosity are listed as follows.

 1. Influence of Solution Concentration

 For Sodium carboxymethylcellulose with whether high, medium or low viscosity, the viscosity will rise with the increase of solution concentration and it is nearly linear with the solution concentration. It is more obvious for high-viscosity Sodium carboxymethylcellulose.

  Table 1 Electric Medium Constant of Sodium carboxymethylcellulose and Other Polymers

Polymer Dielectric Medium	Solvent	Temperature/℃	A	B	C
carboxymethylcellulose	Water	30	136.1	9.71	70.0
	20% Propylene Glycol	30	104.7	6.83	81.0
	40% Propylene Glycol	30	83.4	4.73	100.0
	60% Propylene Glycol	30	61.4	3.08	192.5
	20% Ethylene Glycol	30	98.0	6.20	78.0
	4% Ethylene Glycol	30	71.4	3.80	56.0
	60% Ethylene Glycol	30	62.5	2.78	125.0
	80% Ethylene Glycol	30	60.0	3.07	240.0
	25.5% Glycerol	30	74.0	4.38	66.0
	59.5% Glycerol	30	44.5	1.30	94.0
	76.5% Glycerol	30	26.4	﹣0.26	106.0
Sodium Alginate	Water	30	94.3	3.22	82.0
Agar	Water	30	22.2	9.21	34.30

2. Influence of pH Value

The viscosity of 1% Sodium carboxymethylcellulose solution reaches the maximum and is also the most stable in pH value 6.5-9.0. Generally speaking, the viscosity won’t have big changes when pH value is within the range of 9.0-11.0. However, when pH value is lower than 6, the viscosity will rapidly decrease, then begin to form carboxymethylcellulose acid, and the latter is complete in pH≌2.5. If the pH value is more than 9, the viscosity will also decrease but relatively slowly in the beginning; if the pH value is more than 11.5, it will begin to rapidly decrease. This is because the association between unsubstituted hydroxyl group and alkaline molecules helps to promote the dispersion of cellulose.

 

3. Influence of Temperature

The viscosity of Sodium carboxymethylcellulose solution will decrease with the rise of temperature. When it cools down, the viscosity will immediately rise again, but permanent viscosity decrease will arise when the temperature rises to a certain extent. The temperature limit is generally recognized as 50℃. It must be pointed out that the viscosity decrease has a close relation to the DS (degree of substitution) of Sodium carboxymethylcellulose. The higher the degree of substitution is, the smaller the influence of temperature on the viscosity will be. When the DS is over 1.2, it will be very stable.

4. Influence of Heating Time

  The viscosity of 1% Sodium carboxymethylcellulose solution will immediately gradually decrease when heated for 20 minutes with various kinds of temperatures, and it is more obvious especially with the temperature over 50℃.

5. Influence of Salts

The existence of various kinds of inorganic salt plasma will reduce the viscosity of Cellulose Gum solution. The influence of salts on the viscosity almost depends on the valence number of cation. When meeting salts of monovalent cation, the solution shows water solubility; when meeting salts of trivalent cation, it shows water insolubility; when meeting salts of bivalent cation, it is in between.