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

Abstract

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 (Fe3O4, CrO2) 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 Fe3O4 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.

Fe3O4-Functionalized κ-Carrageenan/Melanin Hybrid Aerogel-Supported Form-Stable Phase-Change Composites with Excellent Solar/Magnetic–Thermal Conversion Efficiency and Enhanced Thermal Conductivity

“…Among various PCMs, n -alkanes are considered to be the most promising candidates because of their suitable phase-change temperature, high energy-storage density, excellent structural stability, and noncorrosive and nontoxic nature. Nevertheless, the inherent liquid leakage issues of n -alkanes during solid–liquid phase transformation seriously restrict their practical application in TES fields. − To address the liquid leakage defect, form-stable PCM composites are developed via micro/nano-encapsulating PCMs into organic/inorganic shell materials or cross-linking PCMs into polymer networks. − However, the introduction of shell materials or cross-linking agents remarkably decreases the thermal storage density of micro/nano-encapsulated PCMs and cross-linked PCMs. Moreover, the encapsulation and the cross-linking procedure are complex and costly, which limit their practical applications for TES .…”

Visual pressure interactive display of alternating current electroluminescent devices based on hydrogel microcapsules

“…Different functional microcapsules can be obtained by changing the types of core and shell materials. 34–39 Among them, the core material inside the microcapsule can stably store the polar/conductive liquid that excites interactive ACEL luminescence, and the compressive strength, corrosion resistance, heat resistance and other properties of the shell material provide interactive conditions. Once the conditions (pressure, pH, and temperature) under which the shell material deforms or breaks are reached, the functional liquid inside the core material can be released to realize the visual monitoring effect.…”

Effect of Microencapsulated Long‐Chain Chlorinated Paraffin on Flame Retardant of Rigid Polyurethane Foam

“…[21] Microencapsulation technology can efficiently encapsulate the target substance "core material" into a tiny container formed by "wall material", thereby producing a protective effect on the core material. [22,23] The MF as the wall material to cover LCCP can solve the above problems skillfully, which can not only expand the limitations of LCCP as an additive in polyurethane foam application but also improve the thermal stability of LCCP, to achieve the preparation of polyurethane foam with high flame retardant efficiency. To date, several flame retardants have been used to form tiny core-shell structures by microencapsulation technology.…”