Questions. 1
Can the HLB value be calculated to determine the stability of a cosmetic? Is this helpful for formulation design?
HLB value can only roughly determine an emulsifier matching range, and it is necessary to constantly adjust the matching ratio to find the most suitable ratio.
HLB value can only roughly determine whether the emulsifier and oil are reasonably matched, and there are many restrictions on the application of HLB value, which is helpful for formulation design. The specific stability needs to be judged by the stability results.
The HLB value can only roughly predict the type of emulsion to be formed, it cannot give the concentration of emulsifier for optimal emulsification, nor can it predict the stability of the resulting emulsion. The application of HLB value to select emulsifier is a more effective method, but also has certain limitations, in the practical application of other methods need to be combined with reference to carry out.
Questions. 2
Is it true that the higher the HLB value, the better the emulsifying ability of an emulsifier in an oil in water product?
No, there is an optimal HLB value, and the matching of this emulsifier pair needs to be determined according to the required HLB of the oils and fats that you want to emulsify, however, the HLB theory has been less used nowadays because the HLB will change under different environments.
The degree of lipophilicity or hydrophilicity of the surfactant can be judged by the size of the HLB value, the larger the HLB value means the more hydrophilic, the smaller the HLB value means the more lipophilic.
It is not the case that the higher the HLB, the better the emulsifying ability, the higher the HLB, the easier it is to dissolve in cold water, but also with reference to the emulsifier’s group, the hydrophilic and lipophilic value of the emulsifier and the emulsification of the oil phase has a certain degree of fit, and not all oils have the same surface tension; theoretically, the relative surface tension of the oil phase is small, it will be less easy to be emulsified, each type of oil to the emulsifier has a certain HLB range to achieve the optimal emulsion state. Each oil has a certain HLB range for the emulsifier to achieve the best emulsification state, add low HLB value emulsifier to form emulsifier pairs, so that the emulsion formed is more stable.
Questions. 3
HLB is hydrophilic-lipophilic balance, hydrophobicity is considered by CPP, so can the hydrophilic end also be considered?
It is true that the hydrophilic end can also be considered when selecting a surfactant. The hydrophilicity and lipophilicity of a surfactant go hand in hand, and the balance between the two affects the performance of the surfactant. Here are some hydrophilic considerations:
Hydrophilic component: The molecular structure of a surfactant usually contains a hydrophilic head group and a lipophilic tail group. The hydrophilic head group usually interacts with water molecules and helps to disperse and solubilize aqueous phase components.
Aqueous Phase Stability: The hydrophilic end of the surfactant can help stabilize the aqueous phase, making the aqueous dispersion system more stable. In emulsifier-based products, the appropriate hydrophilic component can contribute to the formation of fine, uniform water droplets.
Solubility: The hydrophilic portion of a surfactant can contribute to its solubility in water, making it easier to mix with aqueous ingredients.
Wettability: The hydrophilic portion of the surfactant improves the wetting of the surfactant on solid surfaces and helps to reduce the surface tension of the liquid.
Ingredient compatibility: The hydrophilic portion is more compatible with other water-phase ingredients (e.g., water-soluble actives, humectants, etc.), which contributes to stable formulations.
Questions. 4
Is it okay to discuss the HLB value of an epimer in a non-aqueous solvent such as n-heptane toluene? Does it make sense?
Although the definition of HLB value is based on the aqueous phase, the HLB value of a surfactant in a non-aqueous phase can still be used to guide the selection of an appropriate surfactant. In non-aqueous solvents, more attention will be paid to the lipophilicity of the surfactant because in this environment the surfactant primarily needs to be compatible with the non-aqueous solvent. Lower HLB values of surfactants are usually more suitable for lipophilic solvents in the non-aqueous phase.
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