Flame-Retardant and Antibacterial Waterborne Polyurethane Composites Based on a Cu(II)–Phytate–Aromatic Schiff Base Complex

Waterborne polyurethane (WPU) has promising application prospects in paints and coatings owing to its low volatile organic compounds (VOCs), excellent abrasion resistance, and mechanical properties. However, WPU is highly flammable, and there is a high demand for its antibacterial properties in practical applications. To date, effectively suppressing melt dripping remains a challenge during combustion and imparts a high antibacterial property to WPU without compromising the inherent mechanical property. Herein, we report WPU composites on the basis of a Cu(II)–phytate–aromatic Schiff base complex prepared from an aromatic Schiff base derivative, copper(II) acetate, and green and renewable phytic acid. The resultant WPU composites achieved a limiting oxygen index (LOI) of 27.5%. In the UL-94 test, they achieve a UL-94 V-0 rating with no molten droplets and self-extinguish within 1 s after the first and second flame applications. Meanwhile, smoke emission is effectively inhibited in the cone calorimetry test. Moreover, the WPU composites exhibit a killing rate of 99.9% against Staphylococcus aureus and Escherichia coli and excellent tensile toughness, providing a useful reference for designing and fabricating flame-retardant and antibacterial WPU composites.