Layered double hydroxide based polymer nanocomposites

Nanocomposites based on polymers and inorganic filler materials not only create enormous interest among researchers because of their unique way of preparation and properties, but also promise development of new hybrid materials for specific applications in the field of polymer composites. The present article deals with the application of a relatively new class of inorganic materials, namely layered double hydroxides (LDHs), as nanofiller for synthesizing polymer-based nanocomposites. LDHs are mixed metal hydroxides of di- and trivalent metal ions crystallized in the form similar to mineral brucite or magnesium hydroxide (MH) with the incorporation of interlayer anionic species. Several procedures for the synthesis of LDHs, their organic modification, and the synthesis of polymer/LDH nanocomposites are discussed in detail with reference to work done in very recent years. The potential of LDHs, especially magnesium and aluminum-based LDHs (Mg-Al LDH) as nanofillers for the polymer matrix has been investigated. The important aspects in characterizing such hybrid materials (i.e., morphological analysis and melt rheological behavior) have been reported in detail to understand the nature of LDH particle dispersion and its influence on the melt flow behavior of the nanocomposites. The specialty of LDHs as nanofiller is their thermal decomposition behavior, which makes them potential flame retardants for polymers. This aspect has been reported in detail in the case of polyethylene-based systems, where the flame retarding efficiency of organically modified Mg-Al LDH alone and also in combination with conventional flame retardants has been discussed.