Expandable Graphite for Flame-Retardant Polyurethane Foams

Abstract

Intumescent materials, like expandable graphite (EG), inorganic acids, polyols, and their combinations, have gained considerable attention because of their exceptional flame-retardant properties and are being extensively used in various polymeric systems, including coatings and blends. The foamed multicellular char generated by heating the polymer-EG system acts as a physical barrier on the surface of the polymer and reduces the heat and mass transfer rates between the system and its surroundings, thereby acting as a flame-retardant coating. EG is a graphite intercalation compound that is generally produced via oxidation or electrochemical treatment of graphite flakes in an intercalating acid. The present chapter sheds light on the mechanism by which EG induces flame retardancy in polyurethane-based materials like foams and coatings. An in-depth discussion on the mode of action, the chemical and physical changes in the polymer matrix because of EG incorporation, and the major bottlenecks has been provided. © 2021 American Chemical Society. All rights reserved.