Layered Double Hydroxides: An Emerging Class of Flame Retardants

Layered double hydroxides (LDHs) are a class of synthetic clays with brucite [Mg(OH)₂]-like cationic layers containing anions in the hydrated interlayer for charge balance. Due to their tunable chemistry and high charge density, LDHs have received great attention in recent years within the polymer community where the influences of LDHs on the crystallinity, thermal stability, and combustion behavior of polymers have been focal points. This chapter summarizes some of the recent developments in the synthesis of LDHs, their morphology, and physical properties, followed by a brief discussion on various routes to prepare polymer-LDH composites and an overview of their flame retarding behavior in various thermoplastic and thermoset polymer matrices. Overall, this chapter shall serve to keep the reader abreast of the latest developments in the flame retardancy of LDH-based polymer composites, provide a mechanistic understanding of their flame retardancy, and highlight the potential of LDHs as a greener flame retardant.