Cloud Point Determination

Turbidity point refers to the temperature when the non-ionic surfactant is heated in an aqueous solution until the solution changes from transparent to turbidity, reflecting the balance ratio between the hydrophilic and lipophilic relationship of the surfactant molecules. Turbidity point is one of the main indexes to predict the surfactant, and the suitable temperature can be determined by the determination of turbidity point.

GB/T559-2010 specifies five methods (A, B, C, D and E) for determining the turbidity point of non-ionic surfactants according to different types of non-ionic surfactants. Methods A, B and C are suitable for the determination of turbidity points of non-ionic surfactants prepared by the condensation of fatty alcohols, aliphatic amines, fatty acids, fatty acid esters and alkyl phenols with ethylene oxide. Methods D and E are suitable for the determination of turbidity points of non-ionic surfactants formed by block polymerization of ethylene oxide and propylene oxide. For non-ionic surfactants polymerized from fatty acids or fatty acid esters of lipophilic compounds with ethylene oxide - propylene oxide blocks, method E is generally not applicable, but should only be used if the determination has been shown to be reproducible.

The selection of various methods shall follow the following methods.

Method A: If the aqueous solution of the sample becomes turbid between 10 and 90℃, it is determined in distilled water.

Method B: If the aqueous solution of the sample becomes cloudy at less than 10℃ or the sample cannot be fully dissolved in water, the determination is performed in 25% diethylene glycol butyl ether aqueous solution. This method is not suitable for some samples with low ethylene oxide content and samples insoluble in 25% diethylene glycol butyl ether solution.

Method C: If the aqueous solution of the sample becomes cloudy at higher than 90 ° C, it should be measured in a sealed ampoule. Sealing the ampoule allows the operation to be carried out under pressure, reaching temperatures higher than the boiling point of the solution at atmospheric pressure. Sodium chloride aqueous solution can also be used instead of distilled water, and the turbability point of the sample is determined according to method A, but the results are not simply correlated with the results measured by ampoule method.

Method D: If the acidic aqueous solution of the sample becomes cloudy between 10 and 90℃, it is determined in the HCl standard solution with a concentration of 1.0moL.

Method E: If the acidic solution of the sample becomes cloudy at a temperature higher than 90℃, it is determined in an aqueous solution containing 50g n-butanol and 0.04g calcium ions per liter.