Silicon-modified surfactants and wetting: III. The spreading behaviour of equimolar mixtures of nonionic trisiloxane surfactants on a low-energy solid surface

Abstract

The spreading behaviour of binary and ternary equimolar mixtures of siloxane surfactants of general formula [(CH3)3SiO]2CH3Si(CH2)3 (OCH2CH2) nOCH3, n = 3–9, has been investigated. The mixtures show a pronounced temperature dependence on the initial spreading rate. Mixtures imitating the average oligoethylene glycol chain length n = 5 are the fastest spreaders at 15 °C. At 23 °C and 40 °C these mixtures spread fastest sucking n = 6 and n = 8, respectively. For a given average chain length an increasing length difference between the components of the binary mixtures reduces the initial spreading rate. Nevertheless, substantial differences between the phase transition temperature Tc from the lamellar phase (Lα) into the two-phase state (2Φ) and the actual spreading temperature are tolerated. A clear relation between phase transition temperature Tc and initial spreading rate does not exist. Copyright © 1999 John Wiley & Sons, Ltd.