Preparation of a robust and stable superhydrophobic coating with self-cleaning and mold resistance properties on natural bamboo substrate

Bamboo, as an excellent natural material, has received widespread attention and application. However, its defects, including hydrophilicity and poor mold resistance, shorten its service life. Therefore, the best strategy to address the defects of bamboo is to prepare robust and stable superhydrophobic surfaces. This study reports a simple two-step method to prepare superhydrophobic surfaces, using only two materials: rosin and nano-CaCO3. The method is easy to operate, replicable, cost-effective and safe. The prepared superhydrophobic bamboo (SHB) has a water contact angle (WCA) of 153 +/- 3 degrees. After being soaked in water at 0 degrees C, 20 degrees C, 40 degrees C, 60 degrees C, 80 degrees C and 100 degrees C for 2 h, the WCA of SHB maintained superhydrophobic in a wide range of 0-80 degrees C. After being soaked in water at 100 degrees C for 2 h, the WCA of SHB sightly decreased to 147 +/- 3 degrees. After 2000 circles of weight friction, the WCA of SHB was 151 degrees. After 1000 circles of tape peeling, the WCA of SHB was 150 degrees. The WCA of SHB was greater than 151 +/- 2 degrees after soaked in acidic or alkaline solutions with pH values of 3, 5, 7, 9 and 11 for 2 h. After 6 weeks of fungal culture, the infection rate of SHB was 0%, while the infection rate of clean bamboo (CB) was 100%. In a word, SHB not only has good robustness, chemical stability, high and low temperature resistance, and mold resistance, but also can self-cleaning the dust on superhydrophobic surfaces through liquid droplets.