Polyurethane Nanocomposites Based on Layered Double Hydroxides: A Review on Their Syntheses and Applications

Nowadays, polymer nanocomposites have attracted much attention in research activities due to their high mechanical strength, high thermal stability, low-cost, with possibility for their applications in many areas. Polyurethanes (PUs), as a main group of polymers, show a diverse and controllable range of physical and mechanical properties due to their tailored properties depending on the nature of precursors like polyols and isocyanates. This diversity and controllability of their properties make different types of PUs (elastomers, fibers, foams, hydrogels, and coatings) preferred candidates for a variety of uses, including transportation, clothing, furniture, and biomaterials. Many studies have been performed on polyurethane nanocomposites using different types of nanostructures such as graphene-like nanosheets, carbon nanotubes, metal oxides, and so on. Layered double hydroxides (LDHs) are eco-friendly layered mineral nanostructures with positively charged layers and anion-exchange capability. Depending on the types of anions and structure of layers, the LDHs nanostructures can be used broadly for the applications such as catalysts, drug delivery, separation technology, and also as a UV absorbent, corrosion, and a flame inhibitor for polymers. Recently, LDHs nanostructures are used in the fabrication of polyurethane nanocomposites to improve their mechanical, thermal, and flame properties. In this review, in addition to the description of LDH nanostructures, polyurethanes and their applications, LDH-based polyurethane nanocomposites are discussed in detail.