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Department für Chemie - Arbeitsgruppe Prof. Strey

A guide to formulation and application of low-surfactant microemulsions in cleaning processes

Dr. Anna Klemmer, 2014

 

Cleaning processes be they textiles, car or dish washing are taken as a very simple matter. However such processes are highly complex if to be optimised. Most stains and soils bear a broad variety of alkyl chain lengths or pigments, which often are resinated and thus even more complicated to remove. For use of surface active agents in a most sophisticated and eff ective way microemulsions are the systems of choice. Microemulsions are thermodynamically stable, macroscopically isotropic, nano-structured mixtures of at least three components. Their most remarkable feature is their ultra-low interfacial tension which is the driving force behind all eff ective cleaning processes. This thesis gives a general guideline for formulation and application of a microemulsion for a variety of diff erent, partially demanding applications. Generally speaking, three directions concerning cleaning formulations for diff erent applications can be identi ed: water-, oil-rich and balanced microemulsions. In all cases the nearness or the passage through the state of ultra-low interfacial tensions is the key to success while using the lipophilic sponge principle that was developed as part of this work. Water-rich applications like laundry detergency strictly limit the choice of surfactants and other ingredients for environmental reasons. The proposed guideline was applied to this challenge resulting in a 250% e fficiency increase compared to the current top brands at surfactant concentrations below 1 wt %. Moreover, the formulation could be modi ed such that by specifi c usage of phase inversion during the washing long-term stable nanoemulsions could be produced by a low energy method. The resulting nanoemulsions have been systematically analysed with time-resolved scattering techniques and turned out to be stable for weeks, thus easily enhancing stain removal by preventing a redeposition of the material during washing. Oil-rich, temperature-invariant systems were formulated for the cleaning of highly corrosion-sensitive clockworks. Here the proposed guideline allowed for the adaption of molecules with anti-corrosive properties as surfactants, thereby reducing the number of components in the mixture that turned out to be far more stable than conventional products and thus reusable almost indefe nitely. Regarding the balanced system all components required to be of organic and thus of environmentally friendly origin to be combined as an all-purpose cleaner. Here the proposed guideline allowed for an RME and sodium oleate based formulation that is not only completely biodegradable, but also strong enough to easily remove challenging stains such as lacquer layers from optical parts under ultrasonic waves. Generally speaking, the proposed guideline allows for the speci fic usage of microemulsion properties, thereby improving all formulations while protecting our environment.