No abstract

On the basis of previous results revealing that intersurfactant H-bonds improve foam stability, we now focus on how foams stabilized by two different N-acyl amino acid surfactants are affected by different salts (NaF, NaCl, NaSCN), which can promote or break intersurfactant Hbonds. The chosen surfactants, namely, sodium N-lauroyl sarcosinate (C 12 SarcNa) and sodium N-lauroyl glycinate (C 12 GlyNa), differ only by one methyl group at the nitrogen of the amide bond that blocks intersurfactant H-bonds in the case of C 12 SarcNa. The salts were chosen because they are kosmotropic (NaF), chaotropic (NaSCN), and in between (NaCl) and thus influence the formation of an H-bond network in different ways. Surface tension measurements showed that the addition of salts decreased the cmcs of both surfactants and increased the packing density, as expected. Moreover, in presence of the salts, the head groups of the H-bond forming surfactant C 12 GlyNa were more tightly packed at the surface than the C 12 SarcNa head groups. The effect of the salts on foam stability was studied by analysis of the foam height, the foam liquid fraction, and by image analysis of the foam structure. As expected, the salts had no significant effect on foams stabilized by C 12 SarcNa, which is unable to form intersurfactant H-bonds. In contrast, the stability of C 12 GlyNa-containing foams followed the trend NaF > NaCl > NaSCN, which is in agreement with NaF promoting and NaSCN breaking intersurfactant H-bonds. Surface rheology measurements allowed us to correlate foam stability with surface elasticity. This study provides new insights into the importance of H-bond promoters and breakers, which should be used in the future design of tailor-made surfactants.

We developed a new, innovative foam-based cleaning method with which the amount of detergent can be reduced by up to 90%. In addition, foams generate physical cleaning mechanisms, namely imbibition and wiping. The combination of imbibition and wiping is so efficient that it is sufficient to simply let the foam sit on the surface for a while before removing it by vacuuming. No additional mechanical action is needed! This publication describes how we managed to clean the historic carriages of kings and emperors of past centuries in the “Marstallmuseum” in Nymphenburg Palace in cooperation with the “Bavarian Administration of State-Owned Palaces, Gardens and Lakes”.

Liquid foams of intermediate stability have been shown to be very efficient in the cleaning of sensitive surfaces because of the synergy between imbibition and foam decay. While we quantified these mechanisms for contaminations with liquid oils in our previous work, we show here their extension to oils containing soot particles in an effort to simulate increasingly realistic contaminations. Using foams with a wide range of liquid fractions and with different stabilities, we show that the main cleaning mechanisms remain very similar, with the oil entraining the soot particles. However, we find much less efficient soot removal when the liquid channels of the foams are small enough to hinder efficient transport of the soot particles. K E Y W O R D S cleaning mechanisms, cleaning with foams, model contaminations (oil and soot)

Kunst ist der beste Weg, die Kultur der Welt zu begreifen," sagte Pablo Picasso (1881 -1973). Die Oberflächen von Kunst-und Kulturgütern sind die Gesichter der Kunstwerke. Sie spiegeln unsere Geschichte wider, sind ein wichtiger Bestandteil unserer Identität und müssen erhalten werden. Zentimeter für ZentimeterDie Oberflächen historischer Kunstund Kulturobjekte sind über Jahre hinweg Umwelteinflüssen ausgesetzt. Verschmutzungen beeinträchtigen nicht nur die Optik, sondern greifen auch die Materialien an. Es ist schwierig, solche Objekte zu säubern: Jede Oberfläche erfordert eine spezifisch zugeschnittene Reinigungsmethode, um etwa mineralische Verschmutzungen, Ruß, Gummireste, Pestizide, Fette, Salze oder Fasern zu entfernen, ohne das Kunstwerk zu beschädigen.Diese Arbeit ist derzeit mühsam und zeitaufwendig. Denn die Restauratoren können immer nur wenige Quadratzentimeter mit Wattestäbchen, Lösungsmitteln, Gelen oder Kompressen bearbeiten. Schwer zugängliche Oberflächen und -strukturen lassen sich so oft nur bedingt reinigen.