The hydrophobic character of the surface of human hair is particularly attributed to the lipid components of the epicuticle and to a layer of covalently bound fatty acids. This outer f-layer mainly consists of 18-methyl eicosanoic acid (18-MEA), which is covalently bound to the underlying protein matrix, forming the epicuticle as composite surface structure. Daily weathering and chemical treatments, specifically oxidative bleaching, decrease the hydrophobicity of the outer hair surface drastically. Multiple daily stress, simulated by an automatic test device including shampooing, blow drying and sun light exposure, changed the lipid composition of hair significantly. A marked loss of 18-MEA was observed. Decreasing contact angles are the direct consequence. A new method to determine the "pseudo-static" contact angle on hair was developed. The results correlate with the corresponding data obtained by dynamic contact angle measurements according to Wilhelmy. Besides that, the resorption time of water droplets by the hair surface provides additional information about the intactness of the outer f-layer. Specific proteolipids, which are lipid-modified keratins, are able to reconstruct the surface layer of damaged hair by creating renewed surface hydrophobicity and extending the water resorption time by the hair surface.
|Number of pages||12|
|Journal||Journal of Cosmetic Science|
|Publication status||Published - Mar 2011|
- human hair. surface, analysis, Scanning Force Microscopy, contact angle