Silicon-modified surfactants and wetting: IV. Spreading behaviour of trisiloxane surfactants on energetically different solid surfaces

Abstract

The spreading behaviour of defined trisiloxane surfactants of general formula [(CH3)3SiO]2 CH3Si(CH2)3(OCH2CH2) nOCH3 (n = 3–9) on five different solid surfaces has been investigated. Maximum spreading areas and rates are found on non-polar or slightly polar surfaces of 30 to 40 mN m−1 surface energy. Extremely low or high surface energies substantially reduce the spreading rates. On non-polar surfaces rapid spreading is observed for 1 wt % solutions of the relatively short-chained penta- and hexa-ethylene glycol derivatives. On slightly polar surfaces dilute 0.1 wt % solutions of longer-chained derivatives spread faster. This spreading pattern shift coincides with a change of the phase behaviour. Solutions of Silwet L77 do not prefer one specific surface, since 1 wt % solutions abruptly stop spreading after a few seconds and the maximum spreading rates are found for 0.1 wt % solutions. Therefore, Silwet L77 essentially belongs among the long-chained derivatives. Copyright © 2000 John Wiley & Sons, Ltd.