Water Sorption Isotherms of Surfactants: A Tool To Evaluate Humectancy.
Fundamental experimental data for moisture absorption of non-ionic polydisperse surfactants with differing ethylene oxide (EO) content and variable aliphatic portions were measured at relative humidities between 0 and 95% at 25 °C. Remarkable differences in moisture absorption were observed between surfactant classes but also within one series of surfactants differing in either EO content or the long-chain aliphatic fraction. Both the EO units as well as the entire molecular structure, including also the lipophilic domain, were discussed to account for the humectant activity of surfactants. Water sorption isotherms showed an exponential shape, which was argued to be associated with the formation of a "free" water domain. These humectant properties might be relevant to the behavior of a foliar-applied spray droplet of agrochemical formulation products because the uptake of active ingredients will be enhanced as a result of deferred crystal precipitation.
Department of Botany II, University of Würzburg , Julius-von-Sachs-Platz 3, DE-97082 Würzburg, Germany.
Elisabeth
E
Asmus
Global Formulation Technology, Syngenta Crop Protection , Breitenloh 5, CH-4333 Münchwilen, Switzerland.
Christian
C
Popp
Syngenta Crop Protection AG, Syngenta Crop Protection , Schwarzwaldallee 215, CH-4002 Basel, Switzerland.
Adrian A
AA
Friedmann
Department of Botany II, University of Würzburg , Julius-von-Sachs-Platz 3, DE-97082 Würzburg, Germany.
Katja
K
Arand
Department of Botany II, University of Würzburg , Julius-von-Sachs-Platz 3, DE-97082 Würzburg, Germany.
Markus
M
Riederer
D000327:Adsorption; D015394:Molecular Structure; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry*
D013501:Surface-Active Agents; D014867:Water
Tween; humectant activity; humidity; non-ionic surfactants; oleyl alcohol ethoxylates; polysorbates; water sorption isotherms