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Coating approach for a Phase Change Material (PCM)

Paulo, Bruna Barbon, Andreola, Kaciane, Taranto, Osvaldir, Ferreira, Almerindo D., Prata, Ana Silvia
Powder technology 2019 v.341 pp. 147-156
carnauba wax, chitosan, coatings, cold, contact angle, encapsulation, enthalpy, extrusion, fluidized beds, gum arabic, maltodextrins, melting point, phase transition, powders, sodium alginate, solids, temperature, viscosity
PCMs (Phase Change Materials) go through volumetric variation during the solid-liquid phase transitions. Encapsulation enables the preservation of their thermal efficiency and prevents adherence on the surface where they are applied. For PCM application, particles with high load are desirable, and the coating in fluidized bed represents a scalable way to protect them. However, this process requires PCMs in solid state and, thus, it is restricted to their phase change temperature. Carnauba wax (CW) has a high enthalpy and relatively high melting point value, which can be a promising organic PCM and desirable to be employed in processes of coating. This work aimed to coat CW particles in fluidized bed. Some strategies were adopted to increase the load of wax in a particle and reduce experimental assays of coating. For this purpose, CW particles were produced by cold extrusion and a preliminary selection of potential substances to be used as coating material (chitosan, Eudragit® L30-D55, gum Arabic, maltodextrin and sodium alginate) was performed based on their rheological and adhesive properties. Adhesive property was evaluated through the contact angle between the CW and the coating materials. Suspensions containing sodium alginate and Eudragit® showed the lowest contact angle (θ ≅ 40°), low viscosity, and could restrain the volumetric variation of CW particles (coating efficiency = 55%) under heating at 100 °C for at least 1 h. Coating solutions/suspensions with contact angle above 57° and high viscosity were not effective to coat the particles. This study allowed a successful coating process of CW particles in fluidized bed, with potential application to other PCMs and, consequently, enlarging the range of thermal responsive textile and construction materials, and food packages.