Sponges with flame-retardant and superhydrophobic properties offer a dual advantage by enhancing both environmental protection and fire safety. These advanced materials hold significant potential in industrial applications, particularly in oil spill management, marine pollution mitigation, and wastewater treatment, while also ensuring safety in fire-prone environments (1-3). In this study, a novel multifunctional sponge coating with robust superhydrophobicity, superior flame retardancy, and high chemical stability was developed for efficient oil/water separation. The coating material, synthesized using a polymeric resin composed of silica nanoparticles (SiNPs), polydimethylsiloxane (PDMS), and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), was applied to the sponges via dip-coating to enhance their functional properties.
The superhydrophobicity and oil/water separation efficiency of the coated sponges were systematically evaluated through contact angle measurements and oil absorption tests. The highest recorded water contact angle (152°) was achieved with the PDMS/SiNPs/DOPO formulation, confirming the formation of a highly hydrophobic surface. The coated sponges demonstrated an oil/water separation efficiency exceeding 95%, whereas uncoated sponges exhibited significantly lower oil absorption capacity. The flame-retardant performance was assessed through combustion tests. While the uncoated sponge ignited instantaneously, underwent complete combustion, and left no residual structure, the coated sponge exhibited self-extinguishing behavior within 10 seconds and retained its structural integrity post-combustion. SEM analysis of the char layer revealed the formation of a ceramic-like structure, which acted as an effective thermal barrier, significantly enhancing fire resistance. These findings highlight the considerable potential of the developed sponge coatings in enhancing fire safety and environmental protection for industrial applications.