Efficient Ultrasonic-Assisted Preparation of Nano-Mg(OH)2 to Enhance Polydimethylsiloxane Composite Flame Resistance

In this innovative study, an ultrasonic-enhanced continuous-flow method is introduced for one-step synthesis of hydrophobic hexagonal nano-magnesium hydroxide (MH(nm)). Distinct from traditional heating, it shortens reaction time remarkably and has an excellent higher selectivity (purify MH efficiently). The MH(nm) particles present the optimal polydispersity index (PDI) of 0.368, a 218.75% decrease over commercially available MH(μm) particles. Benefiting from the synergistic outcome between the unique physical effect of nanomaterials and the ultrasonic cavitation phenomenon, the polydimethylsiloxane (PDMS) nanocomposites (SS@MH(nm)/PDMS) with MH(nm) modified by sodium stearate (SS@MH(nm)) present excellent thermal conductivity and hydrophobicity. When 30% SS@MH(nm) and 30% SS@MH(μm) are added to PDMS nanocomposites, 30% SS@MH(nm)/PDMS shows a thermal conductivity of 0.4568 W m⁻¹ K⁻¹, 28.35% higher. Its contact angle is 129.47°, 41.27% larger. THR and SPR decrease by 10.49% and 38.45%, respectively. This work provides a simple, green, and efficient process for the preparation of hexagonal MH(nm) with an ortho-hexagonal shape and uniform distribution, and prevents PDMS combustion-property degradation in humidity, offering high-performance flame-retardant materials for humid-environment electrical equipment, with great application potential.