Abstract
The wetting phenomena of various surfactant solutions using the felt disc were studied in relation to hydrophile-lipophile (H/L) balance. In the case of the nonionic surfactants of a series of POE nonylphenyl ethers, the wetting ability of surfactants depend on HLB number, for which there was an optimum range. Since a surfactant with an HLB number in this range gave a cloud point in aqueous solution in the vicinity of the temperature of wetting test, the balance of surfactant H/L properties may be important in achieving maximum wetting ability.
Ionic surfactants containing branched, or two long-chain alkyl goups such as Aerosol OT usually exhibit high wetting ability. In the pseudo three component system, brine/n-decan/Aerosol OT, the increase in concentration of NaC1 caused the H/L balance of Aerosol OT to shift lipophilically and the three phase region appeared at 0.640.75 wt% of NaCl. Wetting ability improved by the addition of NaCl, and the highest was attained at a certain concentration of NaCl. However, further addition caused it to decrease. Thus the wetting properties of a surfactant can be explained from the standpoint of H/L balance ; that is, the surfactant whose H/L properties are exactly balanced easily gives a three phase region containing the surfactant phase, and lowers considerably the O/W interfacial tention to attain high wetting ability.
