Inclusion of Phase-Change Materials in Submicron Silica Capsules Using a Surfactant-Free Emulsion Approach

Abstract

Microencapsulation of phase-change materials is of great importance for thermal energy-storage applications. In this work, we report on a facile approach to enclose paraffin in mechanically strong submicron silica capsules without the addition of any classical organic surfactants. A liquid silica precursor polymer, hyperbranched polyethoxysiloxane (PEOS), is used as both silica source and stabilizer of oil-in-water emulsions because of its hydrolysis-induced interfacial activity. Hydrophobic paraffin is microencapsulated in silica with quantitative efficiency simply by emulsifying the mixture of molten paraffin and PEOS in water under ultrasonication or high-shear homogenization. The size of the capsules can be controlled by emulsification energy and rate of subsequent stirring. The silica shell, whose thickness can be easily tuned by varying the paraffin to PEOS ratio, acts as an effective barrier layer retarding significantly the evaporation of enclosed substances; meanwhile, the microencapsulated paraffin maintains the excellent phase-change performance. This technique offers a low-cost, highly scalable, and environmentally friendly process for microencapsulation of paraffin phase-change materials.

Hollow Silica Particles: Recent Progress and Future Perspectives

“…The symmetrical supercapacitor assembled using particle-PVA electrolytes showed a specific capacitance value of 147 F g −1 at 0.5 A g −1 [103]. HSPs have also been explored as encapsulation containers for phase change materials (PCMs), in which the particles are filled with the PCM, then the shell keeps the PCM confined and does not allow its free flow when it melts [104][105][106]. PCMs are materials that release or absorb large amounts of energy when changing phases.…”

“…For example, paraffin absorbs energy and converts it into the liquid phase, which converts back to the solid phase with the release of energy. PCMs are commonly incorporated in building materials to lower the heating or cooling costs of buildings [104][105][106]. HSP-based encapsulation of PCMs is a promising method, but further improvements are required to increase the thermal conductivity of the silica-based shell.…”

Expanded Graphite/Paraffin/Silicone Rubber as High Temperature Form-stabilized Phase Change Materials for Thermal Energy Storage and Thermal Interface Materials

“…The other is to microencapsulate PW into core/shell structures. Various types of core and shell materials have been widely explored, including graphene [17,18], polymer shells of PMMA [19], PS [20] and PU [21], and inorganic shells of SiO 2 [4,[22][23][24][25] and CaCO 3 [26], etc. In general, the liquid leakage issue of PW can be effectively prevented by utilizing the compatibility between a polymer and PW, as the polymeric matrix can fix PW by a strong intermolecular force, therefore suppressing PW leaching [27,28].…”

Low cost and scalable method for modifying surfaces of hollow particles from hydrophilic to hydrophobic

“…Hollow silica particles are a unique class of materials that has applications in various elds such as drug delivery, thermal insulation, supercapacitors, battery electrolytes, phase change materials, and superhydrophobic coatings. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] There are several strategies for synthesizing hollow silica particles such as use of polymer templates, polymer micelles, spray drying, ultrasonic spray pyrolysis, viruses, bacteria, and solid silica particles. [15][16][17][18][19][20][21] Although the synthesis of hydrophilic silica particles is well developed, several applications require hydrophobic hollow silica particles.…”