Page 26 - Polymer-based Nanocomposites for Energy and Environmental Applications

Introduction of polymer-based nanocomposites 5

Polyamide polymers illustrate some special capabilities such as good dimensional
stability, mechanical strength, high heat distortion temperature, good resistance to
chemicals and oxygen, shock and vibration, and also electric insulation [22].
By considering the environmentally issue, biopolyamides are defined as polyamides
that fully or partially derived from renewable resources [24]. One application of
polyamide polymers is flexible films that are applicable for perishable food
packaging [22].
Generally, two ways are carried out for synthesis of polyamides including
(A) polycondensation of divalent amines and carboxylic acid,
(B) polycondensation of difunctional amino acids containing one amine and one carboxylic
acid functionality pertaining to the same molecule [22].
Nylons as prevalent polyamide polymers are introduced based on a numbering system
with a number of carbon atoms among successive nitrogen atoms in the main chain.
Single numbering is referred to polymers derived from amino acids (e.g., nylon 6) and
products that are generated from a diamine. Also, a dibasic acid is depicted by two
numbers in which the first number shows the number of carbon atoms contributed
by the diamine and the second one represented the number of carbon atoms provided
by the dibasic acid [23]. Klata et al. [25] produced glass fiber/polyamide 6 (GF/PA6)
composites from hybrid yarns. In this study, PA6 multifilament and staple polyamide
fibers were used as thermoplastic materials. da Paz et al. [26] prepared
nanocomposites by polyamide 6/Brazilian organoclay through melt intercalation
and studied the thermal, mechanical, and also thermomechanical factors.

1.2.3.2 Polypropylene and polyethylene matrixes
Polypropylene (PP) is one type of thermoplastic that has been grown to its special
characteristics such as low cost and density, versatile physical properties, and high
heat distortion temperature (HDT) [27]. These properties are pointed to the produced
polymer chains and the building block monomers [28]. In some cases, polyethylene
(PE) is mixed with polypropylene to enhance physical properties, such as elimination
of costly synthesis for new block copolymers and low-temperature impact
performance [29]. Generally, polypropylene contains three main types with different
properties including homopolymers, PP blocks copolymers, and PP random copoly-
mers. PP is carried out for a huge variety of applications such as spun-bonded
nonwovens, fibers, and tapes [28].
In general, thermal, chemical, mechanical, and biological are distinguished as
degradation processes. Polymer degradation is a common problem that is discussed
in several researches. In this process, the loss of volatile components (smoking) or
the loss of mechanical properties has resulted [28]. One of the polypropylene
applications is for food packages and containers. This is due to resistance of this
polymer against biodegradation, enzymatic degradation, or microbial degradation that
causes some important environmental threats, as named “white pollution” [30].
Kamrannejada et al. [30] investigated the photocatalytic degradation of carbon-coated
TiO 2 nanoparticles in polypropylene-based nanocomposites. The observation showed