Flame-retardant, flexible vermiculite–polymer hybrid film

Abstract

Flame-retardant, flexible polymer thin film and coating materials are in large demand for various applications. Three approaches have been attempted: inherently fire-retardant polymers; chemically modified polymers; and the addition of fire retardants as additives for polymers. The first two approaches are based on specific polymers, limiting their wide applications. The last approach provides great flexibility in designing materials with multifunctional properties. Herein, we report the fabrication of a flexible vermiculite–polymer hybrid film with very low flammability through photo-cross-linking of polyethylene glycol network incorporating micronized vermiculite particles. Vermiculite is a thermally insulating agent that can withstand flame up to about 1200 °C. The film fabrication process is very simple, time-efficient, and thickness-controllable. Despite quick processing of the film, vermiculite particles are uniformly distributed within the polymer network. Direct fire testing proves that, at a vermiculite concentration of about 75 wt%, the films of 20 μm thick can withstand actual fire for more than a minute. Without vermiculite, the polymer film is burnt out immediately when in contact with flame. This study demonstrates that a vermiculite–polymer hybrid film, though it is relatively thin and highly flexible, can suppress the heat flow without decomposition for more than just a brief moment when in direct contact with flame.