Bamboo, a fast-growing plant from Asia, is used as building material with unique properties, while exhibiting fast degradation due to its hydrophobicity. Therefore, many attempts have been implemented using several technologies for bamboo modification to alter the hydrophobicity. Most previous studies producing superhydrophobic properties are conducted by using tetraethoxysilane (TEOS) as a precursor agent. However, this method, using TEOS with harmful properties and unaffordable compounds, requires many steps to accomplish the experimental method. Therefore, this paper employed geothermal solid waste as a silica source of the precursor. Thus, an effective and efficient method was applied to prepare superhydrophobic coating by using a precursor of geothermal silica and further modification using hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMCS). The research was executed by the full factorial statistical method using two numerical variables (HMDS/TMCS concentration and silica concentration) and one categorical variable (solvent types). The uncoated material revealed higher weight gain in mass and moisture content than that of the coated bamboo after the soil burial test to assess the durability of the bamboo. However, the durability of superhydrophobic coating realized hydrophobic performance for both agents during sand abrasion for a total of 120 s at an angle of 45°. Statistical results showed the optimum contact angle (CA) achieved in superhydrophobic performance with lower silica concentration for HMDS concentration and the appropriate solvent of n-hexane for HMDS and iso-octane for TMCS. All results were supported using many instruments of analysis to confirm the step-by-step alteration of geothermal silica to be used as a superhydrophobic coating, such as XRF, XRD, FTIR, SEM, and SEM EDX.
Keywords: HMDS; TMCS; bamboo coating; geothermal silica; statistical.