Characterization of modified elastomer surfaces by wetting

Surface and interface phenomena play a very important role in many technical processes, including bonding and coating processes, surface printing, friction and wear behavior. A well-known natural surface phenomenon is the lotus effect, which can be attributed to the surface microstructure and hydrophobic properties of epicuticular waxes [1]. The design and surface structures are an important factor in the development of dirt-repellent surfaces. Applications of (super)hydrophobic surfaces are self-cleaning roofing tiles, textile surfaces, coatings [2], hoses, seals and profiles [3], as well as icephobic coatings [4]. Previous studies have shown that contact angle hysteresis values, which represent a measure of the roughness and chemical heterogeneity of a surface, correlate well with roughness factors for different smooth and rough coated elastomers [5-7]. Roughness parameters such as Ra (arithmetical mean roughness) are mainly used for the quantitative characterization of the roughness of smooth surfaces (1-10 μm) [8-9]. To address this issue, contact angle hysteresis values of surface modified elastomers were compared with roughness parameters obtained from white light interferometry measurements. Future work provides the investigation of rough elastomer and polymer surfaces (Ra >50 μm) in order to compare surface descriptors (cut-off lengths and fractal dimensions) [10] with hysteresis values from contact angle measurements (modified Wilhelmy balance technique). Furthermore the characterization of samples with varied roughness and chemical heterogeneity is of particular interest to get a better understanding of wetting processes of elastomer surfaces.

1. M. Yamamoto, N. Nishikawa, H. Mayama, Y. Nonomura, S. Yokojima, S. Nakamura, K. Uchida. Langmuir, 2015, 26, 7355
2. J. Drelich, A. Marmur. Surface Innovations, 2013, 2, 211
3. A. Wildberger, H. Geisler, R. H. Schuster. KGK rubberpoint, 2007, 60, 24
4. K. Golovin, S. P. R. Kobaku, D. Hyun Lee, E. T. DiLoreto, J. M. Mabry, A. Tuteja. Science Advances, 2016, 2, 3
5. C. W. Karl, M. Klüppel. Chem. Listy, 2011, 105, 233-CL-12
6. C. W. Karl, A. Lang, A. Stoll, A. Weiße, M. Stoll, M. Klüppel. KGK rubberpoint, 2012, 65/4, 44
7. C. W. Karl, W. Rahimi, A. Lang, U. Giese, M. Klüppel, H. Geisler. KGK rubberpoint, 2018, 09, 19
8. S. Palzer, C. Hiebl, K. Sommer, H. Lechner. Chemie Ing. Technik, 2001, 73, 1032
9. L. Busse, K. Peter, C. W. Karl, H. Geisler, M. Klüppel. Wear, 2011, 271, 1066
10. Y. Nonomura, E. Seino, S. Abe, H. Mayama. J. Oleo Sci., 2013, 8, 587