Superhydrophobic and phosphorus‑nitrogen flame-retardant cotton fabric

In recent years, various functions including electrical conductivity, superhydrophobicity, magnetism, flame retardancy and antibacterial activity have been considered to allow cotton fabric (CF) a wider the application range. A new strategy for the preparation of superhydrophobic and flame-retardant CF is described here. Phytic acid (PA) and 1-[3-(trimethoxysilyl)propyl]urea (UPTMS) were firstly coated on CF to provide phosphorus‑nitrogen flame retardancy. Then silica particles grafted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) for the construction of surface roughness and further improvement of flame retardancy and low-surface-energy polydimethylsiloxane (PDMS) were covered on the surface of CF, and the superhydrophobic and flame-retardant CF (SFR-CF) was obtained after thermal curing. The SFR-CF displayed a high water contact angle of 155.9° and excellent anti-adhesion properties and self-cleaning capabilities. In addition, the SFR-CF could be used to efficiently separate oil-water mixtures with a separation efficiency of up to 96.1%. Moreover, the SFR-CF possessed outstanding flame retardancy. The damage length in vertical burning test was only 5.2 cm. This was attributed to not only the release of non-flammable gases such as NH3 and H2O to dilute the concentration of the flammable gas and retard the combustion speed, but also the formation of a dense protective char layer promoted by the presence of poly-phosphoric acid from PA and DOPO-silica. The method used is facile and efficient, and the fabricated superhydrophobic and flame-retardant CF has great potential in a wide range of applications such as oil-pollution treatment, firefighter clothing, outdoor tents and fold-top cars.