Multifunctional polyurethane sponge coatings with excellent flame retardant, antibacterial, compressible, and recyclable properties

Polyurethane (PU) sponge has a wide range of applications in our daily life. Unfortunately, the PU sponge is highly flammable and becomes a breeding ground for bacteria, thereby threatening human health and life. To date, it remains a challenge to improve the flame retardant and antibacterial properties of PU sponge simultaneously without destroying its inherent elasticity and flexibility. Here we report a novel composite coating on the PU sponge using bioderived phytic acid and sodium lignosulfonate via a facile soaking method. Compared to the pristine sponge, the coated PU sponge can reach a 32% reduction in peak heat release rate during cone calorimeter test, and prevent melt dripping after being ignited by a butane torch and the flame can be self-extinguished after the torch is removed. The resultant composite coating also demonstrates a killing rate of 99% against Staphylococcus aureus. Meanwhile, the coated PU sponge can retain the inherent elasticity and flexibility even after 500 cycles of compression. Furthermore, the coating materials are easily recyclable, which provide a useful reference for multifunctional treatment of sponge and cyclic utilization of resources.