7. What does the HLB value of surfactants mean? How is it calculated? What significance does it have for the production of additives?
Answer: In order for a surfactant to be adsorbed on the interface and exhibit unique interfacial activity, it must have a certain balance between the hydrophobic group and the hydrophilic group. This reflects the balance degree of the hydrophobic group and the hydrophilic group. Griffin, an American Atlas research institute, first created it in 1949 and called it HLB (Hydrophilic Lipophilic Balance). The HLB value of surfactants is specified to be 1 to 40, and the HLB value of nonionic surfactants is 1 to 20. The larger the HLB value, the stronger the hydrophilicity. The transition point from lipophilic to hydrophilic is 10. The HLB value of ionic surfactants is between 1 and 40. The HLB value of paraffin, which has no hydrophilicity at all, is 0; the HLB value of oleic acid is 1; potassium oleate is 20; sodium lauryl sulfate is 40; propylene glycol monostearate is 3.4; glycerin monostearate is 3.4. Fatty acid ester is 3.8.
There are many methods for calculating HLB values. Here are some commonly used methods:
① Calculation of HLB value of non-ionic surfactants. The formula derived by Griffin is:
②Calculation of HLB value of ionic surfactant. For anionic surfactants and cationic surfactants, the above calculation method cannot be used, because the hydrophilicity of the hydrophilic groups of anionic and cationic surfactants is higher than that of non-ionic surfactants.
The application of the HLB value of surfactants is closely related to the properties of the surfactant. However, so far, the method of determining the HLB value is still relatively rough, and the surface activity cannot be determined solely by the HLB value. Therefore, the HLB value cannot be used as the main criterion for selecting surfactants, but the HLB value can help us generally understand the properties of surfactants and help with preliminary selection. When compounding additives, it can be considered that their HLB values should be basically the same. The relationship between HLB value and surfactant properties and uses is shown in Table 6-4.
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