Preparation of High-Efficiency Flame-Retardant and Superhydrophobic Cotton Fabric by a Multi-Step Dipping

Cotton fabric, as an important material, is suffering from some defects such as flammability, easy pollution and so on; therefore, it is important to make a flame-retardant and superhydrophobic modification on cotton fabric. In this study, we demonstrated a preparation of high-efficiency flame-retardant and superhydrophobic cotton fabric with double coated construction by a simple multi-step dipping. First, the fabric was immersed in branched poly(ethylenimine) (BPEI) and ammonium polyphosphate (APP) water dispersions successively, and then immersed in polydimethylsiloxane (PDMS)/cellulose nanocrystals (CNC)-SiO2 toluene dispersion to form a BPEI/APP/PDMS/CNC-SiO2 (BAPC) composite coating on the surface of the cotton fabric. Here, the hydrophobic modified CNC-SiO2 rods were used to construct the superhydrophobic layer and the BPEI/APP mixture was used as the flame-retardant layer, as well as SiO2 particles which could further improve the flame-retardant effect. PDMS was mainly used as an adhesive between the BPEI/APP layer and the CNC-SiO2 layer. The resulting cotton fabric shows outstanding flame-retardant properties, in that the value of oxygen index meter (LOI) reaches 69.8, as well as excellent superhydrophobicity, in that the water contact angle (WCA) is up to 156.6°. Meanwhile, there is a good abrasion resistance, the superhydrophobicity is not lost until the 16th abrasion cycles and the flame retardant retains well, even after 100 abrasion cycles in an automatic vertical flammability cabinet under a pressure of 8.8 kPa.