Nowadays, natural rubber (NR) is extensively applied in medical‐healthcare devices. A clogging or bacterial attachment onto product's surface can be avoided by creating the non‐fouling surface for extending the NR utilization. Herein, a superhydrophobic NR film was prepared using two‐step surface modification involving sulfuric acid (H2SO4)‐catalyzed hydration to form hydroxyl (OH) functional groups on the rubber surface followed by grafting with methyltrichlorosilane (MTCS). From X‐ray photoelectron spectroscopy analysis, the immersion of a vulcanized NR film (VNR) in 75 wt% H2SO4 solution for 1 h showed the highest area portion of OH groups on the VNR surface (50.9%), which were expected to act as the active sites for grafting with MTCS via hydrolysis and polycondenzation to obtain a VNR‐OH‐MTCS film. As a measure of the hydrophobicity, the water contact angle (WCA) of the VNR‐OH‐MTCS film prepared by using 2 wt% MTCS concentration was greatest at 155° with a high roughness of 1790 nm. The glass transition temperature and antimicrobial activity of the VNR film were not affected by these surface modifications. This indicated that the superhydrophobic VNR‐OH‐MTCS film maintained the flexibility with ability to inhibit the formation of a bacterial biofilm. Not only superhydrophobicity, the VNR‐OH‐MTCS film also had oleophilicity (oil absorption capacity [k] of 1.13) suggesting that it could be applied for oil/water separation with high separation efficiency of 98.6%. Moreover, the VNR‐OH‐MTCS film still had high hydrophobicity with WCA of 138°–142° after 20 abrasion cycles using a sandpaper under the weighting load not over than 50 g.
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