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Proceedings of the 5 Manufacturing Engineering Society International Conference – Zaragoza – June 2013
Classification of phase change materials and his behaviour in
SEBS/PCM blends
D. Juárez (1), R. Balart, S. Ferrándiz, M.A. Peydró
(1)
Instituto de Tecnología de Materiales, Universidad Politécnica de Valencia, Alcoy (Spain),
[email protected]
ABSTRACT
Phase change materials (PCMs) have the capability of storing heat (latent heat
storage units) and phase transition point to the environment of the operating
temperature. The purpose for which they are designed is to prevent heat loss by
absorption or release thereof. This study analyzes the different classifications of
phase change materials available at industrial level, and the SEM characterization of
SEBS/PCM blends.
Keywords: phase change materials, PCM, SEBS/PCM blends
1. Introduction
Phase change materials (PCMs) have the capability of storing heat (latent heat storage units) and phase
transition point to the environment of the operating temperature. The purpose for which they are
designed is to prevent heat loss by absorption or release thereof.
A PCM classification based on their composition [1] is detailed in Table 1:
PCM Type
ORGANIC
Composition
PARAFFIN COMPOUNDS
Compounds without PARAFFIN
INORGANIC
EUTECTICS
Hydrated salts
METALLIC
ORGANIC - ORGANIC
ORGANIC - INORGANIC
INORGANIC - INORGANIC
The PCM has properties that make them very attractive for the storage of thermal energy.
The state of the art is more developed during low and medium temperature than in high temperature.
There is ample scope for the R & D in terms of PCM screening (selection), micro/macroencapsulation,
the development of new materials and storage systems. Fallahi and Fang [2-4] prepared microPCMs
based upon different types of paraffins and analyze their thermal behavior.
Hadam [5] discusses the transfer of heat during the melting of a phase-change material, determining the
spread and inclination of the solid-liquid interface at the time. Alkan [6] studied the preparation,
characterization and thermal properties of a microencapsulated PMC for thermal energy storage.
Microencapsulated Once the PMMA, then analyzes SEM microscopy and infrared FT-IR, thermal analysis
by calorimetry DSC and thermogravimetric TGA, concluding in good thermal potential.
Alvarado and Bukovec [7-8] come equally to performance microPCMs analysis with DSC and TGA
techniques. Huang [9] studied the improvements made by a 3D model analysis with phase change
materials and compare the results with those provided by previous 2D model. Finally, in a longer term,
research in nanofluids and nano-PCM can be a significant advance through the application of PCMbased technologies.
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Proceedings of the 5 Manufacturing Engineering Society International Conference – Zaragoza – June 2013
2. Classification
A PCM classification, based on the size of the capsules [10], may be the following:
• MicroPCMs
• MacroPCMs
2.1. MicroPCMs
Microencapsulation may be defined as the process of surrounding or wrapping one substance to
another substance at very limited scale, producing capsules ranging from less than one micron to
several hundred microns in size. The microcapsules may be spherical, with a continuous wall
surrounding the core, while others are asymmetrical and with varying shapes, with a number of droplets
of core material incorporated throughout the microcapsule. The three states of matter (solid, liquid and
gas) can be microencapsulated. This allows materials in liquid and gas phase can be manipulated more
easily than the solid state, and can afford a certain level of protection to personnel handling hazardous
materials.
They provide a solution to the increasing consumer demand for improved energy efficiency and thermal
regulation. The PCM substance is typically a paraffin or fatty ester acid that absorbs and releases heat in
order to maintain a defined temperature. Regardless of the state (liquid or solid) of the PCM, the
capsule remains in the solid state, because it is a very stable and inert polymer.
Microencapsulation can be accomplished by many techniques, based for the purpose to arise.
Substances can be microencapsulated with the intention that the base material is confined within the
capsule walls during a specific period of time. Moreover, the core materials can be encapsulated to be
gradually released through the capsule walls, known as controlled release or diffusion, or when external
conditions cause breakage of the capsule walls, melt or dissolve (Figure 1).
Core: PCM in the solid state
Capsule Coating
When the PCM solidifies,
heat energy is
returned to ambient
Temperature rise
PCM capsules photomicrograph
Temperature drop
Capsule Coating
By melting, the PCM absorbs
heat energy
Core: PCM in the liquid state
Figure 1. Functional diagram of the microencapsulated phase change materials (PCM).
The encapsulated substance may be called core material, active ingredient, agent, filler, payload, core or
internal phase. The material used for encapsulating the nucleus is known as a coating, membrane, shell
or wall material. The microcapsules may have a wall or tanks arranged in several layers with different
thicknesses of the base.
Its typical features are:
• Any color.
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Proceedings of the 5 Manufacturing Engineering Society International Conference – Zaragoza – June 2013
• Temperatures available: adjustable ranges on request.
• Form: Dry or wet filter cake. The filter can be diluted further to suit its application.
• Average particle size: microns.
• Stability at elevated temperatures.
2.2. MacroPCMs
MacroPCMs are spherical capsules of a larger size (3-5 mm) containing high concentrations of phase
change materials.
These materials were originally developed for use in cooling vests and clothing. They regulate body
temperature of individuals working in hot environments, such as soldiers in missions in the desert.
The macroPCM absorbs heat excess and allows the user for a longer time in a more comfortable
temperature. The particles are typically charged into the vests, on the inside, which is in contact with
the skin. However, most applications are emerging.
Its typical features are:
• Any color.
• Temperatures available: adjustable ranges on request.
• Form: spherical solid balls.
• Average particle size: mm.
Macroencapsulation technology uses a dual encapsulation process layer, creating a capsule with a
matrix-shaped configuration. Figure 2 shows the arrangement of the PCM macrocapsule.
Figure 2. Schematic representation of a macrocapsule of phase change material (MacroPCM).
3. Microencapsulated product applications
The microencapsulated materials applications are almost limitless. Microencapsulated materials are
used in agriculture, pharmaceuticals, food, cosmetics and fragrances, textiles, paper, paints, coatings,
and adhesives, printing applications, and many other industries.
Historically, carbonless copy paper was the first commercial product to use microcapsules. A
microencapsulated colorless ink layer applied to the top sheet of paper, and a developer material is
applied to the following sheet. When pressure is applied to the writing, the capsules broke and the ink
reacts with the developer to produce the dark color of the copy.
Applications in the textile sector
Nowadays the textile industry uses microencapsulated materials to improve the properties of the
finished products. A growing application is incorporating materials with microencapsulated phase
change (PCM). The phase change material absorbs and releases heat in response to changes in ambient
temperatures. When the temperature increases, the phase change material melts, absorbing heat
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Proceedings of the 5 Manufacturing Engineering Society International Conference – Zaragoza – June 2013
excess, and it feels great. By contrast, when the temperature drops, the PCM solidifies and releases
heat and feels warm. This characteristic of microencapsulated phase change materials can be used to
increase the level of comfort for users of sports equipment, military equipment, clothing, bedding,
building materials, and many other consumer products. Microencapsulated PCMs have even been used
in thermal protection systems patented by NASA (National Aeronautics and Space Administration) for
spacecraft.
Recently, Grahremanzadeh [11] discusses improving the surface properties of fabrics based on
microPCMs incorporating wool, observing a higher thermal activity, increased durability and improved
fiber performance.
Choi [12] studied the changes in the temperature of the tissues treated with PCMs in cold and
temperate, and objectively analyzing subjective sensations supported.
Zhang [13-14] studies PCMs heat storage in thermoregulation nonwoven fibers.
Encapsulation of pesticides
Some pesticides are encapsulated to be released over time, allowing farmers to apply less often, instead
of requiring highly concentrated and toxic pesticides with initial application followed by repeated
applications provided to combat the loss of efficiency due to evaporation or degradation. Protecting
pesticides of total exposure to the elements decreases the risk to the environment (and protected from
being exposed to chemicals) and provides a more efficient strategy for pest control.
Encapsulated in the pharmaceutical sector
Some varieties of oral and injectable pharmaceutical formulations are microencapsulated for release for
longer periods of time or in certain parts of the body. Aspirin, for example, can cause peptic ulcers and
bleeding if the doses are introduced simultaneously. Therefore aspirin tablets are often produced by
compression of quantities of microcapsules which slowly release aspirin through their packaging,
diminishing the risk of damage in the stomach.
Microencapsulation in the construction industry
In the construction industry, the microPCM are incorporated into the construction materials, to increase
the energy efficiency of commercial and residential buildings. These materials are used in combination
with radiant heat and solar energy to enhance the efficiency of the heating and cooling systems. The
microPCM are also being incorporated into walls, plaster, insulation, fiber board, tiles, tile, roofing, etc.
Hasse [15] conducts the embodiment, numerical modeling test boards and containing a phase change
material under conditions of air and water.
Microencapsulation in Storage and transport
In storage and transport, microPCMs are a great alternative to the expensive transport refrigeration or
dry ice. The microPCMs can be incorporated into the biomedical sample containers, pharmaceutical
products, perishables, food samples and laboratory chemicals sensitive to temperature during transport.
Microencapsulation in electronics
In electronics can be used for cooling electronic components in computers, higher duty cycles in lasers,
and help maintain a constant temperature of scientific instrumentation and military equipment used in
the field.
Microencapsulation in automotive industry
There are new applications such as the automotive sector, where Kim [16] studied the feasibility of a
new cooling technique that uses a phase change material for an engine. This new cooling system
contributes to a substantial reduction in cooling system in terms of volume and performance.
Microencapsulation in telephony
Similarly, in mobile telephony, Setoh [17] examined the cooling of mobile phones that use a phase
change material (PCM), performing mobile experimental prototypes made of aluminum. The study
indicates that the use of heat sinks with PCMs was effective for cooling of mobile phones in the
intermittent moderate usage.
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Proceedings of the 5 Manufacturing Engineering Society International Conference – Zaragoza – June 2013
Wutting [18] proposed to incorporate PCMs in flash memory cooling, following the recent replacement
of hard drives (computing) for these devices.
4. Results and Discussion
Among the classification of different phase change materials available at industrial level, the micro PCM
can be considered ideal for incorporation as an additive to thermoplastic materials due to its size, with
the aim of improving energy efficiency and temperature control, being key the analysis of the possible
modification of the polymer mechanical characteristics and the maximum permissible degree of
saturation.
As prior work has proceeded to MPCM/SEBS mixtures characterization. The morphological study of
micro elements encapsulated value performed by SEM analysis. In Figure 3, shows the distribution of
the capsules and their different size distributions. It characterization performed for PCM 28D, with a
melting temperature of 28 º C, in the center the microencapsulated 37D with a melting temperature of
37 ° C and finally, the last sample of 52D with a melting temperature of 52 º C
Figure 3 .- SEM characterization of PCM 28, 37, 52 D samples
It has also carried out a DSC test, in order to determine what fusion values obtained compared with the
programmed values. The performing results of this differential scanning calorimetry (DSC) on the
various types is shown in Table II.
Table II. Thermal values obtained in the DSC test
PCM samples
Peak Tª (ºC)
Normalized Integral
(J·g-1)
PCM28D
30,9
-143,04
PCM37D
39,9
-170,41
PCM52D
54,4
-129,75
The thermal characterization development by DSC mixtures has been conducted with the three PCM:
MPCM28D, and MPCM52D MPCM37D. In the figure 4, it can be seen that applying several cycles of
heating, cooling and reheating, the PCM showing reacts to melt peaks preprogrammed temperatures
without appreciable variations..
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Proceedings of the 5 Manufacturing Engineering Society International Conference – Zaragoza – June 2013
Figure 4- DSC PCM 37D characterization
Similarly proceeded with mixtures doped with MPCM28D and MPCM52D 0%, 1%, 2%, 5% and 10% by
weight, showing a similar pattern, but refers to melting / crystallization corresponding (about 28 ° C and
52 ° C respectively)
We have also carried out a characterization of SEBS / PCM blends with different grades of PCM. In this
case maintaining the same polymer matrix. We can see that the fracture that presents the material
allows for the seamless integration of PCM in the polymer matrix.
Figure 5. SEM of SEBS/PCM mixtura characterization.
It clearly shows the correct embedding of the microcapsules into the matrix PMC SEBS. This is
representative for a good adherence of the microcapsules of PCM in the SEBS blend as a good wet
distinguished from the microcapsules. Moreover, as noted in the previous figures, even with high
percentages of PCM, the fracture surface does not show many particles, and this is indicative that are
occluded within the polymer matrix.
4. Conclusions
The use of encapsulated materials with phase change (PCM) is an efficient method for the thermal
effects of regulation in heating and cooling systems.
The micro PCM can be considered ideal for incorporation as an additive to thermoplastic materials due
to its size.
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Proceedings of the 5 Manufacturing Engineering Society International Conference – Zaragoza – June 2013
In the tests performed can be seen that the PCM shows a high thermal stability for use in several cycles
as indicated in the DSC tests. The blend of SEBS / PCM shows good wetting of the matrix PCM, allowing
the mixture to stabilize the subsequent transformation process.
5. Acknowledgements
Authors thank “Ministerio de Ciencia y Tecnología”, Ref: DPI2007-66849-C02-02 and Generalitat
Valenciana FPA/2010/027 for financial support.
6. Referencies
[1].
Pérez, Á. d. P., "Situación y Futuro de los PCM (Phase Change Material)", Centro de Desarrollo
Tecnológico - Fundación LEIA, (2010).
[2].
Fallahi, E., Barmar, M. and Kish, M. H., "Preparation of Phase-change Material Microcapsules
with Paraffin or Camel Fat Cores: Application to Fabrics", Iranian Polymer Journal, 19:(4), 277-286
(2010).
[3].
Fang, G. Y., Li, H., Liu, X. and Wu, S. M., "Experimental Investigation of Performances of
Microcapsule Phase Change Material for Thermal Energy Storage", Chemical Engineering & Technology,
33:(2), 227-230 (2010).
[4].
Fang, Y. T., Kuang, S. Y., Gao, X. N. and Zhang, Z. G., "Preparation of nanoencapsulated phase
change material as latent functionally thermal fluid", Journal of Physics D-Applied Physics, 42:(3), (2009).
[5].
Hamdan, M. A. and Al-Hinti, I., "Analysis of heat transfer during the melting of a phase-change
material", Applied Thermal Engineering, 24:(13), 1935-1944 (2004).
[6].
Alkan, C., Sari, A., Karaipekli, A. and Uzun, O., "Preparation, characterization, and thermal
properties of microencapsulated phase change material for thermal energy storage", Solar Energy
Materials and Solar Cells, 93:(1), 143-147 (2009).
[7].
Alvarado, J. L., Marsh, C., Sohn, C., Vilceus, M., Hock, V., Phetteplace, G. and Newell, T.,
"Characterization of supercooling suppression of microencapsulated phase change material by using
DSC", Journal of Thermal Analysis and Calorimetry, 86:(2), 505-509 (2006).
[8].
Bukovec, N., Bukovec, P. and Arbanas, V., "TG AND DSC INVESTIGATION OF CACL2.6H2O, A
PHASE-CHANGE MATERIAL FOR ENERGY-STORAGE", Thermochimica Acta, 148:(281-288 (1989).
[9].
Huang, M. J., Eames, P. C. and Norton, B., "Comparison of predictions made using a new 3D
phase change material thermal control model with experimental measurements and predictions made
using a validated 2D model", Heat Transfer Engineering, 28:(1), 31-37 (2007).
[10].
Microtek Laboratories, I., "Phase Change Materials", Microtek Laboratories, Inc., (2010).
[11].
Ghahremanzadeh, F., Khoddami, A. and Carr, C. M., "Improvement in Fastness Properties of
Phase-Change Material Applied on Surface Modified Wool Fabrics", Fibers and Polymers, 11:(8), 11701180 (2010).
[12].
Choi, K., Chung, H. J., Lee, B., Chung, K. H., Cho, G. S., Park, M., Kim, Y. and Watanuki, S.,
"Clothing temperature changes of phase change material-treated warm-up in cold and warm
environments", Fibers and Polymers, 6:(4), 343-347 (2005).
[13].
Zhang, X. X., Wang, X. C., Zhang, H., Niu, J. J. and Yin, R. B., "Effect of phase change material
content on properties of heat-storage and thermo-regulated fibres nonwoven", Indian Journal of Fibre &
Textile Research, 28:(3), 265-269 (2003).
[14].
Zhang, Y. W. and Faghri, A., "ANALYSIS OF FORCED-CONVECTION HEAT-TRANSFER IN
MICROENCAPSULATED PHASE-CHANGE MATERIAL SUSPENSIONS", Journal of Thermophysics and Heat
Transfer, 9:(4), 727-732 (1995).
[15].
Hasse, C., Grenet, M., Bontemps, A., Dendievel, R. and Sallee, H., "Realization, test and
modelling of honeycomb wallboards containing a Phase Change Material", Energy and Buildings, 43:(1),
232-238 (2011).
[16].
Kim, K. B., Choi, K. W., Kim, Y. J., Lee, K. H. and Lee, K. S., "Feasibility study on a novel cooling
technique using a phase change material in an automotive engine", Energy, 35:(1), 478-484 (2010).
th
Proceedings of the 5 Manufacturing Engineering Society International Conference – Zaragoza – June 2013
[17].
Setoh, G., Tan, F. L. and Fok, S. C., "Experimental studies on the use of a phase change material
for cooling mobile phones", International Communications in Heat and Mass Transfer, 37:(9), 1403-1410
(2010).
[18].
Wuttig, M. and Steimer, C., "Phase change materials: From material science to novel storage
devices", Applied Physics a-Materials Science & Processing, 87:(3), 411-417 (2007).