Page 705 - Polymer-based Nanocomposites for Energy and Environmental Applications

648 Polymer-based Nanocomposites for Energy and Environmental Applications

lower peak stress compared with neat epoxy composites. This has been attributed to
the imperfections of the cross-linked structure in the presence of CNC. CNC/epoxy
composites showed lower modulus and higher peak stress for neat epoxy compared
with ionized CNC. However, ion-exchange CNC shows higher modulus and peak
stress when compared with Na-CNC. The improved modulus is a consequence of
decreased self-aggregation of CNC in the presence of imidazolium or phosphonium.
Regarding the water absorption ability, ion-exchange CNC exhibits only 10% larger
absorption ability, while Na-CNC is 50%. A similar observation has been established
with CNC polystyrene composites. Despite the better desperation property, the lower
aggregation of the ion-exchange CNC has been the key factor for improved
transparency [39].
It is to say that 1,2,3-trimethylimidazolium CNCs (Me3lmCNC), 1-hexyl-2,-
3-dimethylimidazolium CNCs (HxMe2lmCNC), and methyl(triphenyl)phospho-
nium-exchanged CNCs (MePh3PCNC) are more hydrophobic than Na such that
dispersive surface energy decreases within normal temperature and atmosphere; the
lower dispersive surface energy may benefit the desperation of the CNC into the poly-
mer; therefore, ion-exchange CNC can be easily dispersed into epoxy and polystyrene.
However, when the relative humidity is increased, dispersive surface energy does not
change significantly for exchanged ion, but it decreases for Na-CNC [39].
From the overview of cellulose nanocrystal and its behavior, it can be concluded
that compare with two most important materials: glass and carbon nanofibers. CNCs
have picked up much attention around us along with their various applications and
improved mechanical properties [52]. And most importantly, it plays a key role into
the nanocomposites area, while the term renewable comes forward slightly [53].

24.3.3 Silica nanoparticles

Silica nanoparticle (SiO 2 ) is the combination of silicon (46.83%) and oxygen
(53.33%) [54]. As a filler, it has been proved that coating with SiO 2 (silicon dioxide
or silica nanoparticle) in commercial epoxy resin has great significance to enhance
the performance wind turbine blade surfaces under superhydrophobic condition
[55]. Silica nanoparticle is an excellent choice for making nanocomposites for poly-
mers as well [56].
Due to the unique combination of silica nanoparticles, it has a wide range of capa-
bilities to provide a significant improvement in different properties like mechanical
and thermal including some features like coatings, biotech, and catalysis and so on.
But coatings with nanosilica have brought extensive attention to several industries
[57]. Moreover, SiO 2 as filler has a great significance to improve performances of
numerous composites. For example, it has been proved that by adding silica
nanoparticles to the epoxy resin with 10%, it improves the fatigue life performances
of glass fiber-reinforced plastic (GFRP) composites [58]. Also, with a few silica
nanoparticles (0.3%) in epoxy resin, it has brought a maximum of 16% improvement
of interfracture strength including maximum rate of fatigue life cycle [59].
Fatigue behavior of GFRP that has to be enhanced is also a great matter of concern
while coming to the point of increasing the life cycle of the wind turbine [59]. Fracture