Transparent hydrophobic fire-resistant nitrogen–phosphorus–silicon coatings self-assembled via in-situ polymerization

For the cables applied in humid environments, the service life will be shortened due to moisture. Thus, it is necessary to develop a coating on the surface of cables that possesses good hydrophobicity and high fire rating. Here, based on the synergy of organic nitrogen, phosphorus, and silicon, a hydrophobic flame-retardant silicon coating was prepared by the introduction of low organic nitrogen and phosphorus through covalent bonding. At first, DHQI was prepared from DOPO-HQ and IPTS by the reaction between -NCO and -OH. Then prepolymers of coatings were prepared by hydrolysis of various functional silanes and DHQI, and the coating from the prepolymer is characteristic of flower-like microstructure by the self-assembled DHQI, resulting in high water contact angle (up to 101°). At the same time, the flame retardancy of PP with SR-DHQI coating is of UL-94 V-0 rating. Compared with PC, PHRR of PC with SR-DHQI-2 coating is reduced by 40.1%, and facing the butane spray gun flame impact, the fire resistance time of PC with the coating is twice of that of PC, indicating that the coating can protect the substrate from melting and prevent the spread of flames, which is associated with the gas and condensed phases flame retardancy, derived from the synergistic effect of N and P from DHQI. This work provides a feasible and sustainable strategy for the establishment of multifunctional protective coating on the cables.