Effect of MgAl-layered double hydroxide exchanged with linear alkyl carboxylates on fire-retardancy of PMMA and PS

Alkyl carboxylate-modified layered double hydroxides (LDH) were prepared and used as nanofillers for poly(methyl methacrylate) (PMMA) and polystyrene (PS). The LDH intercalated with long-chain linear alkyl carboxylates (CH ₃(CH₂)_nCOO^-, n = 8, 10, 12, 14, 16, 20) were prepared via anionic exchange of MgAl-nitrate, showing a systematic increase in basal spacing with longer alkyls. MgAl-undecenoate LDH was prepared by co-precipitation. The MgAl-LDHs were melt blended with poly(methyl methacrylate) and bulk polymerized with styrene to form nanocomposites. The dispersion of the MgAl-LDH in the polymers was investigated by transmission electron microscopy and X-ray diffraction. Thermal and fire properties were studied using cone calorimetry and thermogravimetric analysis; the thermal stability of both polymers was enhanced and a very significant reduction in the peak heat release rate was observed for almost all of the poly(methyl methacrylate) composites and a few of the polystyrene composites.