Layer-by-layer assembly of efficient flame retardant coatings based on high aspect ratio graphene oxide and chitosan capable of preventing ignition of PU foam

• Published in: Polymer degradation and stability Vol. 152; pp. 1 - 9
• Main Authors: Maddalena, Lorenza, Carosio, Federico, Gomez, Julio, Saracco, Guido, Fina, Alberto
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.06.2018; Elsevier BV
• Subjects: Assembly; blood platelets; calorimetry; Chitosan; coatings; combustion; Embedding; finishes; Flame retardancy; Flame retardants; Flammability; foams; Graphene; Graphene oxide; heat; Heat release rate; High aspect ratio; Hydrogen bonds; Ignition; infrared spectroscopy; Layer-by-Layer; melting; Multilayers; Nanoparticles; Platelets (materials); Polymers; Polyurethane foam; Polyurethane foams; Protective coatings; Smoke; Surface chemistry; Thermal stability; Layer-by-Layer; Flame retardancy; Graphene oxide; Chitosan; Polyurethane foams
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2018.03.013

The layer-by-layer (LbL) technique is adopted for the construction of multilayers encompassing chitosan and graphene oxide (GO) platelets capable of improving the flame retardant properties open cell PU foams. The LbL assembly follows a linear growth regime as evaluated by infrared spectroscopy and yields a multilayer structure where GO platelets are embedded within a chitosan continuous matrix. 3 and 6 bi-layers (BL) can efficiently coat the complex 3D structure of the foam and substantially improve its flame retardant properties. 3BL only add 10% to the original mass and can suppress the melt dripping during flammability and reduce both the peak of heat release rate by 54% and the total smoke released by 59% in forced combustion tests. Unprecedented among other LbL assemblies employed for FR purposes, the deposition 6BL is capable of slowing down the release of combustible volatile to the limits of non-ignitability thus preventing ignition in half of the specimens during cone calorimetry tests. This has been ascribed to the formation of a protective coating where the thermally stable char produced by chitosan serves as a continuous matrix embedding GO platelets, which control volatile release while mechanically sustaining the PU foam structure. •The LbL assembly is used to impart flame retardant properties to PU foams.•Chitosan and graphene oxide are employed as coating constituents.•The melt dripping was suppressed during flammability tests.•3 bi-layers allow for a 54% reduction in the peak of heat release rate.•6 bi-layers can slow down volatile release to lower flammability limit.