Page 116 - Polymer-based Nanocomposites for Energy and Environmental Applications

92 Polymer-based Nanocomposites for Energy and Environmental Applications

3.5.3.3 Vermiculite as supporting material for PCM

Vermiculite is a lightweight material with porous structure that is inexpensive and
nontoxic [82]. Therefore, it has been used in TES applications such as construction
and insulation in buildings [4]. Karaipekli and Sari [82] investigated the capric-
myristic acid/vermiculite (CA-MA/VMT) composite as form-stable composite
PCM. The composite PCM can contain up to 20 wt% CA-MA without any leakage
from the composite. The composite exhibited a good thermal and chemical reliability
when subjected to 3000 thermal cycles. Besides, the prepared composite can be suc-
cessfully utilized into mortar and concrete.

3.5.3.4 Montmorillonite as supporting material for PCM

Bentonite or montmorillonite group is a natural industrial mineral [83]. The bentonite
has some advantageous properties such as excellent absorption capacity, low cost, and
good compatibility and chemical inertness with cement, mortar, and concrete, making
it a potential support for the production of form-stable composite PCM [84]. Sari et al.
prepared a novel form-stable composite PCM for thermal energy storage by impreg-
nating capric acid (CA) [84], polyethylene glycol (PEG600), dodecanol (DD), and
heptadecane (HD) into bentonite clay. The maximum weight percentage for CA,
PEG600, DD, and HD in composite PCM was found as high as 40, 43, 32, and
18 wt%, respectively, without showing any leakage problems. The phase-change tem-
peratures were between 4 and 30°C, and the latent heat was between 38 and 74 J/g,
respectively. Moreover, the composites exhibited a good thermal and chemical reli-
ability when subjected to 1000 thermal cycles. Furthermore, the thermal conductivity
was improved by adding 5 wt% of expanded graphite (EG).
Some of the research works focusing on the development of form-stable composite
PCM based on clay minerals are discussed. From this discussion, it can be concluded
that the most common PCMs used to prepare the form-stable composite PCM are fatty
acids and their eutectic mixture and paraffin. Therefore, it is suggested that in the
future, researchers should also focus on applied investigation of form-stable compos-
ite PCM especially in buildings.

3.6 Clay nanocomposites polymer foams

Polymer foams or cellular materials with nanoclays are an intriguing class of materials
with unique structure and properties, as they may offer a combination of the special
characteristics of foams (lightness, improved insulating properties, and sound absorp-
tion, among others) and those given by the incorporation of clay nanoparticle
(improved specific mechanical properties, enhanced thermal stability, reduced gas
permeability, improved flame retardance, etc.) [85]. This class of materials has
recently attracted great interest for applications ranging from thermal insulation to
hydrogen storage, electromagnetic shielding, cushioning, buoyancy, energy absorp-
tion (packaging), sensors, tissue engineering scaffolds, etc. [86].