Page 27 - Polymer-based Nanocomposites for Energy and Environmental Applications

6 Polymer-based Nanocomposites for Energy and Environmental Applications

less photocatalytic degradation with higher amount of carbon content in the TiO 2
nanopowders. In another study [31], the blends of polypropylene (PP) and low-density
polyethylene (LDPE) were evaluated in economically recycling process. Also, Jacob
et al. [32] investigated the effects of silane-coupled agents in the application of
nanoparticles in polypropylene nanocomposite.

1.2.3.3 Liquid-crystal matrixes
Liquid-crystal polymers (LCPs) as a family of thermoplastics contain a highly
crystalline molecular chain rather than other prevalent polymers such as nylon. Thus,
this characteristic makes these polymers nearly linear, semirigid, stacked orientation
of molecules with highly ordered station in the liquid-crystal phase [33,34].The
anisotropy property of LCPs and also susceptibility to separation are due to the
primary bonds within the molecule that makes a high attractive force within the mol-
ecule [33]. In this matter, in case a force is transversely applied to the molecular
orientation, the secondary bonds get most of the load that causes an easier separation.
In contrary, a longitudinal load forces more heavily the primary bonds of the
molecules and leads in a higher difficult separation [33,34].
These polymers show very remarkable properties in severe conditions such as high
heat, electric, and chemical resistance. In this field, PET copolyester, copolyamide,
and polyester-amide are the most common LCPs [33,34]. As another characteristic
of LCPs is their easily injection molded, the LCP melting temperature is 280–330°
C with mold temperatures of 70–130°C [33,34]. LCPs are carried out in the industries
with weight limits on the basis of their thermal stability and remarkable mechanical
properties of fabricated fibers from LCPs [35].

1.2.3.4 Polyurethane matrixes
The German scientist Otto Bayer who is known as father of polyurethane (PU) on
behalf of his coworker developed the polyaddition reaction in 1937. In this process,
the polyaddition of a diisocyanate to a diol with a catalyst reacts to a polyurethane in
mild conditions without the undesired by-products. Consequently, in 1956,
poly(tetramethylene ether)glycol was represented by DuPont via polymerizing
tetrahydrofuran as the first commercially available polyether polyol.
Generally, polyurethane is referred to the chemical family as the urethane
polymers, which are containing of two principal raw materials: isocyanates and
polyols. These parts are mixed together with catalysts and some other additives. In
this process, the final product status depends on types of isocyanates and polyol
constituents that can be illustrated as foam, solid, or liquid.
PUs depict different distinct characteristics such as wide range of hardness,
elasticity of rubber, toughness and durability of metal, hardness of fiberglass, protec-
tion as varnish, and squishy as upholstery foam. Hence, due to this wide range of
performances, PU can be carried out in several fields such as toys, plane wings,
and industrial components with high abrasive resistance. The PU composites are
classified regarding to the density of polymeric matrix and fiber reinforcement.