Contact Persons: I. Lioumbas [lioumbas@gmail.com] , C. Koukiotis [koukiotis@gmail.com]
A. Fundamentals
Aim of this project is to examine how different type of surfactants (i.e. Na-LABSA, TEA-LABSA, SLES, CocoDEA and SDS) and different surfactant concentrations (both above and below the CMC) affect foam destabilization and, in particular, elucidate the interplay between free drainage and bubble size variation. For this, foam destabilization experiments are conducted at varying SDS concentrations where the evolution of liquid fraction and bubbles size is registered simultaneously. Instantaneous volume measurements of the drained liquid and the remaining foam yield the evolution of the global liquid fraction and drainage rate in the foam. Continuous electrical conductance measurements give the local liquid fraction and drainage rate in the foam. Microphotographs allow estimation of bubble size distribution and bubble population at regular time intervals. Our results reveal the significant role of bubble size on the free drainage.
Typical foam images during foam destabilization for various SDS concentrations.
Left axis: Liquid fraction profiles normalized with respect to the initial liquid fraction value, obtained both locally (thick line) and globally (points); thin line coresponds to the global measurements fitting. Right axis: The derivatives of the above presented profiles. The effect of various surfactant concentrations on the above profiles is presented: a. 300ppm, b. 600ppm, c.1000ppm and d. 2000ppm.
We use our expertise in foam stability studies to various industrial projects. Recently we optimized foam properties of commercial detergents. We also achieve in our experiments to formulate safer products for human health by replacing the coconut diethanolamide (CocoDEA) with Coco Amido propyl amine oxide (CAPAO) and keeping at the same time the superior foaming and cleaning properties. CocoDEA is frequently used in many detergent formulations to stabilize foam but there is a noise about its safety for human health. There are publications that frequent use of detergents with CocoDEA may cause allergic contact dermatitis [1] and one study also found that CocoDEA has carcinogenic activity to some species of mices [2].
[1]. Fowler JFJ (1998) Allergy to cocamide DEA. American Journal of Contact Dermatitis 9(1): 40-1 Klein, K., 2004. Evaluating shampoo foam. Cosmetics and toiletries, 119(10), pp. 32-35
[2]. U.S. Department of Health and Human Services, Public Health Service & National Institutes of Health, 2001. TOXICOLOGY AND CARCINOGENESIS STUDIES OF COCONUT OIL ACID DIETHANOLAMINE CONDENSATE, P.O. Box 12233: NIH PUBLICATION No. 01-3969
Stability of foam of optimized detergent recipes at 0.2% actives in tap water.
Stability of foam of optimized detergent recipes at 0.2% actives in tap water in the presence of fatty soil.