Transparent Aqueous Mg(OH)₂ Nanodispersion for Transparent and Flexible Polymer Film with Enhanced Flame-Retardant Property

A transparent aqueous nanodispersion of magnesium hydroxide (MH) is first synthesized by using a rotating packed bed (RPB) reactor. Based on this nanodispersion, we further fabricate a transparent poly(vinyl alcohol) (PVA)/MH nanocomposite with enhanced flame-retardant property by a solution-mixing method. The PVA/MH nanocomposite can keep good transparency even at high MH contents. The limiting oxygen index (LOI) of PVA/MH nanocomposite with 50 phr MH is improved by 45% compared to pure PVA. The peak of heat release rate (pHRR) in the microscale combustion calorimetry (MCC) significantly reduces from 453 W/g for pure PVA to 332 W/g. Importantly, a smooth and compact residue layer for the PVA/MH nanocomposite is formed during combustion, which yields a barrier for the transfer of heat and oxygen. These results indicate that the PVA/MH is an excellent transparent flame-retardant material, which opens a door to manufacture transparent and fire-resistant polymer-based nanocomposites with environmental-friendly process.