Hydrophile-lipophile balance group number

One of the most important characteristics of the emulsifier is its CMC, which is defined as the critical concentration value below which no micelle formation occurs. The critical micelle concentration of an emulsifier is determined by the structure and the number of hydrophilic and hydrophobic groups included in the emulsifier molecule. The hydrophile-lipophile balance (HLB) number is a good criterion for the selection of proper emulsifier. The HLB scale was developed by W. C. Griffin [46,47]. Based on his approach, the HLB number of an emulsifier can be calculated by dividing... 

The selection of different surfactants in the preparation of either O/W or W/O emulsions is often still made on an empirical basis. A semi-empirical scale for selecting surfactants, the hydrophilic-lipophilic balance (HLB number) was developed by Grifhn [18]. This scale is based on the relative percentage of hydrophihc to lipophilic (hydrophobic) groups in the surfactant molecule(s). For an O/W emulsion droplet the hydrophobic chain resides in the oil phase, whereas the hydrophilic head group resides in the aqueous phase. In contrast, for a W/O emulsion droplet the hydrophilic group(s) reside in the water droplet while the lipophilic groups reside in the hydrocarbon phase. 

A useful index for choosing surfactants for various applications is the hydrophilic-lipophilic balance (HLB), which is based on the relative percentage of hydrophilic-to-lipophilic groups in the surfactant molecule(s). Surfactants with a low HLB number normally form W/O emulsions, whereas those with a high HLB number form a O/W emulsion. A summary of the HLB range required for various purposes is given in Table I. 

By the hydrophilic-lipophilic balance (HLB) system, according to Griffin (15). The HLB ratio is expressed as a number based on the emulsifying properties of the emulsifier. The HLB can also be estimated from the chemical structure according to the molecular group contributions, as repeated by Davies (16). HLB numbers are closely related to the functional properties of the emulsifiers. 

The concept of hydrophile-lipophile balance (HLB) was first developed by Griffin [13] to correlate the structure of surfactant molecules with their surface activity. The HLB number (0-20) reflects the hydrophilicity of surfactant, and it increases with increasing hydrophilicity. A general trendi often observed in a family of surfactants is the increased CMC with HLB. Table 2.1 serves as a general guide for the formulator to choose surfactants that are most suited to meet the requirements of end-users. This semiempirical approach has been proved to be quite useful. Davies and Rideal [14] proposed that the HLB value of a particular surfactant could be calculated according to the group contribution approach. 

Davies scale or the hydrophile-lipophile balance, HLB, is an empirical, parameter. HLB number = S(hydrophilic groups) + S(lipophilic groups) + 7. The HLB was originally developed as a scale to classify the relative efifectiveness of nonionic surfactants at forming stable emulsions at room temperature. Surfactants with HLB values between 0 and 4 are water/oil emulsifiers, surfactants with HLB values between 6 and 10 are wetting agents, and surfactants with HLB values between 12 and 18+ are oil/water emulsifiers. 

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