Stacked graphene oxide and bio-sourced polyelectrolyte complexes thin coating for fire safe and sound absorbing flexible foams

Water based approaches aimed at the reduction of open cell foam flammability currently suffer from limited efficiency and practicability. In order to address this issue, this paper exploits the unique features of bio-sourced polyelectrolyte complexes (PECs) and high aspect ratio graphene oxide (GO), to deliver an efficient and high performing solution to foam flammability. To this aim, PECs encompassing gelatin and phytic acid were deposited on a brick-and-mortar graphene oxide polyacrylic acid (PAA) layer. This simple two-step deposition produces a stacked GO-PAA/PECs conformal coating on the 3D structure of the foam. The assembly produces a self-extinguishing behaviour during flammability tests in vertical configuration. The heat release rates are also reduced up to 50 % as assessed by forced combustion tests at 35 kW/m2. This set of FR properties has never been achieved before with such low number of deposition steps. In addition, the sound absorbing properties of the coated foams were evaluated by impedance tube tests, highlighting how these foams could find application as fire-safe sound-absorbing panel. The proposed approach thus represents an efficient step forward in the design of multifunctional fire-safe foams with potential industrial scalability