Enhanced chemical and mechanical durability of superhydrophobic and superoleophilic nanocomposite coatings on cotton fabric for reusable oil/water separation applications

Superhydrophobic polymer nanocomposite coatings based on polydimethylsiloxane (PDMS) and silica nanoparticles were fabricated on the surface of cotton fabrics via a dip-coating technique. The major aim was to illuminate the effect of a proper curing agent on the hydrophobicity of PDMS-based coating on the fabric surface. Employing different ratios of polymer and nanoparticles in the absence/presence of a curing agent resulted in the optimum formulation with enhanced chemical and mechanical durability. Wettability results showed that, at a given composition of polymer and nanoparticles, the addition of curing agent renders the coating superhydrophobic. Morphological analysis revealed that the addition of curing agent caused a much higher adsorption of nanoparticles onto the fabric's surface. Based on X-ray photoelectron spectroscopy results, the coating's top layer was more dominated by silica nanoparticles once the curing agent was added to the formulation. This behavior was attributed to the interlocking of silica nanoparticles within the network of cross-linked PDMS chains in the presence of the curing agent. The combination of superhydrophobicity and superoleophilicity was employed to use the coated fabrics in oil/water separation applications. If a high separation efficiency (> 95 %) is needed, the coated fabric could be re-used for 50 consecutive separation cycles.