Phase change materials (PCMs) based on hydrated salts are promising candidates for energy storage and release applications owing to their relatively high latent heats per volume, their high thermal ...conductivities, and their nonflammability. The use of these PCMs, however, is limited owing to incongruent melting, significant supercooling during crystallization, and irreversible phase transformations. PolyHIPEs, polymers templated within high internal phase emulsions (HIPEs), were proven to be effective at encapsulating aqueous solutions and organic liquids. Here, calcium chloride hexahydrate (CCHH) was successfully encapsulated within elastomeric, acrylate-based, emulsion-templated polymers by using free-radical polymerization within molten-salt-in-oil HIPEs. The effects of adding a nucleating agent to the internal phase to reduce supercooling and the effects of enhancing HIPE stability through modification of the external phase were investigated. The crosslinking and stabilization modifications made to enhance the original polyHIPE formulation successfully enhanced the encapsulation efficiency. The most promising system, 75% CCHH dispersed as relatively uniform internal phase droplets of 100–300 μm in diameter, exhibited melting and crystallization heats of ⁓120 J/g, a relatively low degree of supercooling, and negligible transformation to calcium chloride tetrahydrate. This work, demonstrating that molten salt hydrates can be successfully encapsulated within elastomeric, emulsion-templated monoliths, can be used as a blueprint for the encapsulation of other salt hydrates.
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•Inorganic phase change material (PCM): encapsulated in an elastomeric polyacrylate.•High internal phase emulsions (HIPEs): Molten PCM in 2-ethylhexyl acrylate (EHA).•Nucleating agent: reduced supercooling of calcium chloride hexahydrate PCM.•Polymer nanoparticles: enhanced HIPE stability and thermal energy storage-release.•EHA pre-polymerization & a polymeric crosslinking comonomer enhanced HIPE stability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•Flexible and recyclable aerogels were fabricated from octadecane-in-water emulsions.•The aerogels showed controllable external shapes, robust compression and good encapsulation.•The ...aerogels had excellent heat storage properties, including high heat capacity and reusability.•The aerogels exhibited recyclability, with heat storage properties well preserved.
Although emulsion-based, phase change material-encapsulated monolithic composites are promising for latent heat storage, their rigidity and non-recyclability imposed by the relatively dense covalent crosslinking hinder the composites from real applications. Herein, we report the fabrication of aerogel composites with flexibility and recyclability from cellulose nanocrystal-stabilized, octadecane-encapsulated Pickering emulsions solidified using physical gelation. The resulting monolithic composites exhibited controllable external shapes, and the introduction of poly(vinyl alcohol) significantly reduced the leakage of the encapsulated octadecane. The aerogel composites showed flexibility at temperature over 30 °C, and robust compressive behavior, without fracture at 70% compressive strain. The composites possessed similar heat storage (melting) temperature and heat release (crystallization) temperature to that of bulk octadecane, high heat capacity (up to 253 J.g−1) and high reusability, without obvious deterioration in heat capacity after 100 heating–cooling cycles. Moreover, the aerogel composites exhibited recyclability, simply by dissolving the composites in hot water to form emulsions and then by freeze drying to form aerogel composites. The flexibility and recyclability, together with robust compression, controllable external shapes, high heat capacity and good reusability, make the aerogel composites to be excellent candidates for latent heat storage.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Emulsion-templated porous polymers (polyHIPEs) with highly interconnected voids that range from a few micrometers to hundreds of micrometers are typically synthesized within the external phases of ...high internal phase emulsions (HIPEs), emulsions containing more than 74% internal phase. Recent advances in emulsion-templated polymers include new developments in HIPE formation, polymerization chemistries, macromolecular structures, crosslinking strategies, porous architectures, and surface functionalization. This article focuses upon emulsion-templated polymers through the prism of the research and development work in our laboratory. The innovative emulsion-templated systems described include shape-memory polymers, encapsulation systems, hydrogels, and porous carbons. This article also briefly reviews recent work in the field and draws some conclusions regarding trends and future directions. The abundance of diverse and disparate research directions pursued under the banner of “emulsion templating” is indicative of its high degree of versatility. Novel families of porous polymers with unique properties can now be devised and designed through the advances described herein.
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•Emulsion templating: innovative porous polymers and encapsulating polymers.•Shape memory foams from a crystallizable polyacrylate: uncoated and hydrogel-coated.•Encapsulation: aqueous solutions, inorganic melts, organic liquids.•Hydrogels: pH and/or temperature responsive, superabsorbents, contaminant adsorbents.•Carbons: hierarchical porosity, nitrogen-doping, hydrothermal carbonization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Octodecane-encapsulated, wide-temperature-range flexible composites were fabricated.•The composites showed controllable external shapes, robust compression and good encapsulation.•The composites ...showed high reproducibility, reusability and stability, and extremely high heat capacity.
While phase change material (PCM)-encapsulated, emulsion-templated monolithic composites are promising for latent heat storage, they are usually rigid, which hinders their wide applications. Here, we report the fabrication of PCM (octodecane, OD)-encapsulated, emulsion-templated monolithic composites with wide-temperature-range flexibility for latent heat storage. The composites were prepared from OD-in-cellulose nanofiber (CNF) suspension emulsions through interfacial reaction and subsequent drying. Composites from freeze drying showed flexibility at temperature over the melting point of the encapsulated OD (30 °C), while composites from heat drying were flexible at temperatures even below the melting point of the encapsulated OD (such as at 20 °C). The wide-temperature-range flexibility could result from the reduced bonded OH groups within CNFs and the presence of voids with nanofibrous walls. The two types of the composites showed controllable external shapes, robust compression and good encapsulation, without fracture at a high compressive strain of 70% and without leakage at a compressive strain below 30%. Moreover, the composites possessed high reproducibility, extremely high heat capacity (up to 250 J.g−1, even slightly higher than that of bulk OD), high reusability and stability, without obvious deterioration in heat capacity after 100 heating–cooling cycles. The feature that combines wide-temperature-range flexibility, mechanical robustness, high heat capacity and good reusability/stability enabled the OD-encapsulated monolithic composites to be excellent candidates for latent heat storage.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Bulk hierarchical porous ceramics with unprecedented strength‐to‐weight ratio and tunable pore sizes across three different length scales are printed by direct ink writing. Such an extrusion‐based ...process relies on the formulation of inks in the form of particle‐stabilized emulsions and foams that are sufficiently stable to resist coalescence during printing.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•Emulsion templates were generated with poly-Pickering-HIPE micromixers.•The porosities of the resulting polyHIPEs were depend on the flow rate ratios.•Openness of ...poly-Pickering-HIPEs affects the droplet diameters of emulsions.•Macroporous polymers having graded porosities were fabricated with micromixers.•3D shapes were emulsified, printed and photopolymerised, simultaneously.
Micromixers made from emulsion templated macroporous polymers (poly-Pickering-HIPEs) were used to continuously produce polymerizable high internal phase emulsions (HIPE) by injecting a monomer containing continuous phase and aqueous internal phase into micromixers. The interconnected and complex flow path through poly-Pickering-HIPE micromixers resulted in effective mixing by creating local vortices and shear. The emulsion phase volume fraction of the produced HIPE templates can be varied during the process. PolyHIPEs with a porosity gradient ranging from 74% to 89% were produced by altering the phase volume ratio during emulsification in poly-Pickering-HIPE micromixers. The average pore size of the produced polyHIPEs can be tailored by using poly-Pickering-HIPE micromixers with degrees of interconnectivity ranging from 0.028 to 0.06. The lower the degree of interconnectivity of the micromixer the smaller the droplet size of the produced HIPEs and thus the average pore size of the resulting polyHIPEs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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In the current study we demonstrate a method of preparation of low-density polydimethylsiloxane (PDMS) foams from emulsions by using water-based thixotropic fluids as porogens. ...Aqueous dispersions of synthetic hectorite clay and nanocellulose were used as thixotropic fluids, enabling the preparation of fine emulsions in bulk form with the droplet size down to few tens of microns by simple hand mixing. Contrary to conventional emulsion templating where stabilization of emulsion is required, a strategy was developed for obtaining foams by using controlled destabilization of an emulsion, induced during the curing of the PDMS matrix phase by adding a carefully selected surfactant in optimized concentration. This strategy enables the preparation of bulk PDMS foams with interconnected porosity in a range of density values, fast and deformation-free drying and uniform porous structure with a range of mechanical properties. Clay microplatelet with clearly defined shape and with mass in the nanogram range is retained in spherical pores as the porogen is removed by evaporation. Foams with density down to 0.353 g/cm3 and thermal conductivity of 0.0745 W/m * K were prepared. Elastic modulus of the prepared foams ranged from 0.156 to 0.379 MPa, a reduction of 94.3–86.3% as compared to pure nonporous PDMS.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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