Hydrophilic Lipophilic Balance (HLB value)
Hydrophile-Lipophile Balance (HLB): The combined affinity of hydrophilic and lipophilic groups in a surfactant molecule for oil or water.
HLB value is used to indicate the size of hydrophilic or lipophilic ability of surfactants, the higher the HLB value, the stronger the hydrophilicity, and vice versa, the stronger the lipophilicity. 1949 Griffin put forward the concept of the HLB value, the range of the HLB value of the nonionic surfactant is set at 0-20, the HLB value of the paraffin wax, which is composed of the largest saturated alkane group of the hydrophobicity is set at 0, and the HLB value of the hydrophilic maximum is set at 0, and the hydrophilic maximum is composed of the largest oxyvinyl group of the hydrophilicity. The HLB value of paraffin, which is the most hydrophobic and consists entirely of saturated alkyl groups, is 0, and the HLB value of polyoxyethylene, which is the most hydrophilic and consists entirely of hydrophilic oxyethylene groups, is 20, while the HLB values of the other surfactants range from 0 to 20. With the introduction of new surfactants, more hydrophilic varieties have been used in practice, such as sodium lauryl sulfate, which has an HLB value of 40.
The HLB value of surfactants is closely related to their applications. Surfactants with HLB values between 3 and 6 are suitable for use as W/O emulsifiers, while surfactants with HLB values between 8 and 18 are suitable for use as O/W emulsifiers. As solubilizers the HLB value is 13 ~ 18 ,as wetting agents the HLB value is 7 ~ 9 and as detergents the HLB value is 13 ~ 16 [3]. HLB values of surfactants for different applications
Cloud Point
Cloud Point (CP): The cloud point is the temperature at which phase separation occurs in a homogeneous micellar solution of a nonionic surfactant.
Surfactant aqueous solution, with the increase in temperature will appear turbid phenomenon, surfactant from completely dissolved to partially dissolved, the temperature at which the transition is the cloud point temperature. Turbidity point is a characteristic constant of nonionic surfactants, which is influenced by the molecular structure of the surfactant and the coexisting substances [4].
Critical micelle concentration (CMC)
Critical Micelle Moncentration (CMC): The lowest concentration at which surfactant molecules associate in the solvent to form micelles.
Ionic surfactant micelles are charged micelles formed by ionic aggregates, also called colloidal electrolytes. Nonionic surfactant micelles are not charged and therefore are not colloidal electrolytes. Before and after the critical micelle concentration of surfactant in solution starts to form micelles, some physical properties of the solution, such as osmotic pressure, turbidity, surface tension, conductivity, etc. will change significantly. Therefore, attention must be paid to the use of surfactants, otherwise it will cause the opposite effect. For example, when adding surfactants as water reducing and dispersing effects in refractory castables, the concentration exceeds the critical micelle concentration, but will make the fluidity of the castables worse.
