Biomass-functionalized graphene oxide toward waterborne polyurethane composite with enhanced flame retardancy and hydrophobicity

In this study, phytic acid-polydopamine functionalized GO (GO@PA@PDA) was first synthesized. The DOPO derivatives, hydroxyl-terminated polydimethylsiloxane (PDMS) and GO@PA@PDA were incorporated into waterborne polyurethane (WPU) by in situ polymerization. The chemical structure of GO@PA@PDA was characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, ultraviolet–visible (UV–vis) spectroscopy and scanning electron microscopy. A cone calorimeter test and a universal testing machine investigated the flame retardancy and mechanical properties of GO@PA@PDA modified waterborne polyurethane (GPD-WPU). The results showed that the incorporation of GO@PA@PDA into WPU significantly enhanced the flame retardancy by reducing the heat release rate, total heat release, smoke production rate, and total smoke production. Furthermore, the mechanical properties of the GPD-WPU composite films increased with the dosage of GO@PA@PDA from 0 to 2.0 wt%, and decreased slightly afterward. The contact angle and atomic force microscope measurements showed that the addition of GO@PA@PDA increased the surface roughness of GPD-WPU composite film, thereby improving the hydrophobicity of GPD-WPU composite films. Afterward, GPD-WPU as a finishing agent was coated on polyester fabric. The experimental results of limiting oxygen index (LOI) and the vertical burning test indicated that when the dosage of GO@PA@PDA was 2.5 wt% in GPD-WPU, after-flame time, after-glow time, damage length and LOI value of the coated polyester fabric were 2.9 s, 0 s, 6.8 cm, and 28.6%, respectively. Graphical