Researchers found that by using a modified nano-SiO₂ hybrid medium in combination with a fluorepoxy polymer, a superhydrophobic coating can be created on paper that retains the original properties of the paper.

The research proves that the synergistic modification of paper by organic-inorganic hybrid coatings can create a stable superhydrophobic surface that can be used effectively for oil-water separation. Source: Adobe.Firefly

Most of the super hydrophobic paper surfaces prepared at present will change the original properties of the paper and can not be used for oil-water separation continuously. There is not yet much systematic research on super hydrophobic modification of paper-based materials. The use of polymers and inorganic fillers for synergistic modification is also relatively rare. In this paper, fluo rine-containing epoxy polymer P(GMA-r-DFMA) and KH550 modified nano-SiO₂ were mixed to obtain an organic-inorganic hybrid super hydrophobic solution, which was chemically cross-linked to the surface of paper fibers to form a micro- and nano-thin coating to construct a super hydrophobic surface, but the original properties of the paper remain unchanged. The optimal parameters (polymer concentration, soaking time, drying time, drying temperature) for building super hydrophobic surface on paper were explored, and the optimal conditions are the polymer concentration of 7 mg/mL, soaking time of 5 h, drying time of 6 h, drying temperature of 100 °C.

Under the optimum conditions, the water contact angle of the modified paper surface is 164 ± 2o and the water rolling angle is 5 ± 2o. The surface of the super hydrophobic modified paper contaminated with toner can be self-cleaned by water droplets. Compared with the unmodified paper, the whiteness, smoothness and glossiness of the surface of the super hydrophobic modified paper have not changed greatly. When the oils were n-hexane, n-octane and trichloromethane, the oil-water separation efficiency of the modified paper could reach 99.9 %, 99.9 % and 98 %, and the effects were stable. Super hydrophobic modified paper in water formed a large number of bubbles on its surface, resulting in silver mirror phenomenon. SEM results showed that the pore structure of the paper was not changed after modification. The surface of the original paper fiber is very smooth, but the surface of the super hydrophobic modified paper fiber has a large number of micro and nano protrusions.