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Title:
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Physico-chemical and mechanical properties of microencapsulated phase change material
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Author:
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Giró Paloma, Jessica; Oncins, Gerard; Barreneche Güerisoli, Camila; Martínez, Mònica; Fernández Renna, Ana Inés; Cabeza, Luisa F.
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Notes:
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Microencapsulated phase change materials (MPCM) are well known in advanced technologies for the utilization
in active and passive systems, which have the capacity to absorb and slowly release the latent
heat involved in a phase change process. Microcapsules consist of little containers, which are made of
polymer on the outside, and paraffin wax as PCM in the inside. The use of microencapsulated PCM has
many advantages as microcapsules can handle phase change materials as core allowing the preparation
of slurries. However there are some concerns about cycling of MPCM slurries because of the breakage of
microcapsules during charging/discharging and the subsequent loss of effectiveness. This phenomenon
motivates the study of the mechanical response when a force is applied to the microcapsule. The maximum
force that Micronal® DS 5001 can afford before breaking was determined by Atomic Force Microscopy
(AFM). To simulate real conditions in service, assays were done at different temperatures: with the
PCM in solid state at 25 ºC, and with the PCM melted at 45 ºC and 80 ºC. To better understand the behavior
of these materials, Micronal® DS 5001 microcapsules were characterized using different physic-chemical
techniques. Microcapsules Fourier Transform Infrared Spectroscopy (FT-IR) results showed the main
vibrations corresponding to acrylic groups of the outside polymer. Thermal stability was studied by Thermogravimetrical
Analysis (TGA), and X-ray Fluorescence (XRF) was used to characterize the resulting
inorganic residue. The thermal properties were determined using Differential Scanning Calorimetry
(DSC) curves. Particles morphology was studied with Scanning Electron Microscopy (SEM) and Mie
method was used to evaluate the particle size distribution. Samples had a bimodal distribution of size
and were formed by two different particles sizes: agglomerates of 150 lm diameter formed by small particles
of 6 lm. Atomic Force Microscopy in nanoindentation mode was used to evaluate the elastic
response of the particles at different temperatures. Different values of effective modulus Eeff were calculated
for agglomerates and small particles. It was observed that stiffness depended on the temperature
assay and particle size, as agglomerates showed higher stiffness than small particles, which showed an
important decrease in elastic properties at 80 ºC.
The work is partially funded by the Spanish government
(ENE2011-28269-C03-02 and ENE2011-22722) and the European
Union (COST Action TU0802). The authors would like to thank
the Catalan Government for the quality accreditation given to their
research group GREA (2009 SGR 534) and research group DIOPMA
(2009 SGR 645). |
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Subject(s):
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-Thermal energy storage
-Microencapsulated phase change material
-Atomic force microscopy |
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Rights:
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(c) Elsevier, 2012
info:eu-repo/semantics/restrictedAccess |
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Document type:
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article
publishedVersion |
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Published by:
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Elsevier
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