Green organic-inorganic coatings for flexible polyurethane foams: Evaluation of the effects on flame retardancy, antibacterial activity, and ideal mechanical properties

Abstract

Flexible polyurethane foams (FPUFs) have high flammability accompanying with massive heat release and toxic smokes containing -NCO groups and HCN release, resulting in causing serious pollution and threatening human lives. Therefore, it is necessary to reduce the toxic products release while endowing FPUFs with flame retardancy. In this work, phosphorylated chitosan (PSPLCS) was prepared through an eco-friendly, cost-effective and simple process, and paired with ZnO to form the films which acted well with excellent flame retardancy, smoke suppression and antibacterial properties on FPUFs. FPUF-PSPLCS/Zn3 self-extinguished and reached up to the UL-94 V-0 rating, the PHRR value decreased by 59%, and the char residues at 700 °C significantly enhanced. By investigating the released products during the thermal degradation and the structure of char residues, the flame-retardant mechanism was concluded that the decreased production of flammable and toxic gases resulted in burning asphyxiation, and denser char layers established exceptional heat and O2 barriers. Furthermore, FPUF-PSPLCS/Zn3 exhibited 99.99% antibacterial rates on both Escherichia coli and Staphylococcus aureus. Fortunately, the coatings had barely affected the mechanical properties. The flame-retardant and antibacterial FPUFs have been successfully prepared, and this work proposes a new and easy tread for the construction of multi-functional coatings.