Page 100 - Polymer-based Nanocomposites for Energy and Environmental Applications

76 Polymer-based Nanocomposites for Energy and Environmental Applications

The PCMs have properties that provide several advantages over other technologies
such as a high latent heat per unit weight, melt concurrent, little or no supercooling, no
or less volume change during solid-liquid phase transition, low vapor pressure, and
high heat of fusion that is melting and solidifying at a certain temperature [6].
Finally and as mentioned previously, PCMs are useful materials enabling the stor-
age and restitution of large amounts of energy storing and releasing large amounts of
energy with slight or no temperature change. They have good thermal and chemical
stability for long operating times. They are not toxic and widely available.
This book chapter focuses on the different types of phase-change materials (PCMs)
and their different properties. Among several kinds of measurement techniques of
PCMs, only those used in the construction field are covered in this chapter. Subse-
quently, the present book chapter deals with some routes for incorporating PCMs into
building materials. In another hand, an outline is given on composite phase-change
material (CPCM) reinforced by nanoclays and their incorporation into insulation
materials of polymer foam type as PCMs.

3.2 Phase change materials

Phase-change materials (PCMs) are a series of functional substances taking advantage
of heat storage materials in a latent form. Generally, they exhibit the thermal energy
transfer that occurs during their phase change from solid state to liquid state or vice
versa. In fact, the concept of the PCMs can be based on the variation of the temper-
ature; generally, the increase in the ambient temperature causes a rupture of chemical
bonds, thereby generating the phase change from the solid to the liquid state. When the
ambient temperature decreases further, the PCM will return to the solid phase with
exothermic decomposition that gives off the absorbed heat. In the other hand, the
PCMs are known by their good heat transfer and their high latent heat of fusion, which
make them very useful in many potential applications [7]. The PCMs possess other
desirable relevant properties not only the thermal ones [8] but also the kinetic, chem-
ical, and economic ones that are presented in the following paragraph.

3.2.1 Properties of PCM
The important properties of a material to be used as PCM are listed in Table 3.1 [1].
However, recent progress in the design and characterization of novel PCMs used as
energy storage materials, including nanomaterials, has opened new opportunities to
enhance the PCM performance. This will be more detailed in the next sections.

3.2.2 Classification of PCM

The PCM classes can be divided into three groups: organic, inorganic, and their eutec-
tic mixture (Fig. 3.1) [9]. In general, the first class called organic PCMs mainly con-
sists of paraffin, fatty acids, esters, and other organic compounds [1]. This class of
materials is chemically stable, noncorrosive, and nonreactive [7]. They also display