Surface engineering of layered double hydroxide (LDH) nanoparticles for polymer flame retardancy

• This paper reports the potential of using hydrothermal synthesis for the fabrication of tailored nanoparticles (LDH).
• LDH surface engineering in a continuous flow manner via on-line post synthesis surface modification approach
• The heat sink action of made-up LDH and its phase transition during thermal decompositions
• This paper highlights the possible use of LDH as a nano-filler with a flame retardant action.

One of the significant impacts of nanotechnology on polymeric material's flammability is the achievement of polymer nanocomposites (PNCs). Layered double hydroxide (LDH) is one of the most promising synthetic clays for PNC fabrication. A novel continuous flow method for LDH synthesis via controlled hydrothermal conditions has been recently reported. This paper reports on fine tuning surface chemistry of LDH via surface modification with different surfactants in a continuous flow manner. LDH surface properties were changed from hydrophilic to hydrophobic, and the developed particles were harvested from the water phase to the organic phase. The synthesized LDH has the potential to deliver a flame retardant action (as a heat sink material) to the hosting polymer by absorbing heat, releasing water, and forming a protective oxide layer which can prevent further degradation. The heat sink action of synthesized LDH was evaluated with thermal analysis techniques. The phase transition of LDH to corresponding oxides during its endothermic decomposition was investigated with XRD. This is the first time LDH has been surface modified continuously and its FR action as well as its phase transition has been examined. This paper might open the route for LDH as nano-filler with flame retardant properties. Surface modification was reported to enhance the dispersion characteristics of inorganic nanoparticles into the hosting polymer. Therefore enhanced flammability performance can be achieved at low solid loading level.

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