Preparation and Performance of Dual-functional Magnetic Phase-change Microcapsules

Graphical Electromagnetic shielding has attracted increasing attention for the purpose of safety and health. However, magnetic shielding materials with phase change insulation properties are less reported. Here, dual-functional magnetic phase-change microcapsules for magnetic shielding were successfully prepared with paraffin as the core, melamine-formaldehyde resin as shell, and nano-magnetic particles dispersed in the shell layer through the in-situ polymerization. Using the screen printing technique, the great magnetic shielding role of these microcapsules ink was demonstrated in both static and pulsed magnetic fields on wallpaper. The fabrication of desired anti-magnetic materials for irradiation shielding remains a challenge to date. In this work, a new type of dual-functional magnetic shielding phase change microcapsules with paraffin as the core, melamine-formaldehyde (MF) resin as the shell and doped with magnetic particles in the shell were successfully prepared by in situ polymerization. The magnetic particles were dispersed in the shell layer by coating a hydrophilic emulsifier on the surface. These microcapsules were specifically applied to the field of magnetic shielding by the screen printing method. The effect of magnetic particles on the performance of phase-change microcapsules was examined by differential scanning calorimetry and thermogravimetric analyses. The magnetic type and magnetic strength of the microcapsules were studied by the vibrating sample magnetometer. Moreover, the effects of different magnetic particles (Fe 3 O 4 , CrO 2 ) on the performance of phase change microcapsules and the magnetic strength of microcapsules were compared. The results showed that these two kinds of magnetic particles can greatly improve the phase change latent heat, thermal stability, and thermal conductivity of the microcapsules. Finally, the great magnetic shielding role of these microcapsules was demonstrated in both static and pulsed magnetic fields through the screen printing of magnetic shielding ink on wallpaper. Incorporating 0.5 g Fe 3 O 4 inside of microcapsules, specifically, the magnetic intensity was effectively reduced by ∼250 Oe within a short distance in the static field. We expect that these magnetic microcapsules hold great potential for the shielding of irradiations via the screen printing on various substrates.