Page 107 - Polymer-based Nanocomposites for Energy and Environmental Applications

Nanoclay and polymer-based nanocomposites: Materials for energy efficiency 83

50µm
Fig. 3.3 Micrograph of the shape-stabilized paraffin [24].

weight and will deform. A similar study was performed by Sari [7] in which two kinds
of paraffin (P1 and P2) were used as a dispersed material and a high-density polyeth-
ylene (HDPE) was used as a supporting material. The maximum weight percentage for
both paraffin types in the shape-stabilized PCM was found as high as 77% without
showing any leakage problems of paraffin. The melting temperatures of both paraffin
types in the shape-stabilized PCMs were determined as 37.8 and 55.71°C, and the
latent heats were found to be 147.6 and 162.2 J/g, respectively. Furthermore, to
improve thermal conductivity of the PCM, 3 wt% of expanded and exfoliated graphite
was added to the composite. Thus, the thermal conductivity was increased by around
(14%–24%) for the two studied PCMs.

3.3.5 Form-stable composite PCM

The form-stable and the shape-stabilized PCMs are currently the focus of much sci-
entific research. These materials have been prepared to overcome the problems of
leakage and lower thermal conductivity of the pure PCMs that limited their extensive
application [26]. In addition, they do not need any encapsulating containment, thereby
saving the cost. The form-stable composite PCM can be developed by two methods:
natural immersion and vacuum impregnation [7]. The first one is easy and simple to
use, but the retention capacity of porous building materials to store thermal energy is
low. Therefore, it can be increased through the second method [27]. Several vacuum
impregnation equipment have been used to develop the form-stable composite PCM.
One of them is shown in Fig. 3.4 [28].