84
4 PVA Bionanocomposite Films with Different Particle …
10 wt%, optical [3], mechanical [4], thermal [5], electronic [6] and antimicrobial [7]
properties can be remarkably enhanced in polymer nanocomposites, while some key
features of net polymer systems remain such as low density and high processibility
[2]. Such polymer nanocomposites have a wide range of applications in range of
aerospace engineering, automotive components and medical devices [1]. The effective reinforcing mechanism is based on a fundamental concept that the chain mobility
of polymeric molecules is restricted by rigid nanofillers according to matrix–particle
interfacial interactions in polymer nanocomposites [2, 8]. The specific areas associated with matrix–filler interactions are known as interfacial regions with completely
distinct properties from nanoparticles and polymer matrices alone. More importantly, the material performance of polymer nanocomposites primarily depends on
the volume of interfacial regions and properties [8] in relation to critical nanofiller
factors such as nanoparticle shapes and structures.
In addition to a major concern of nanoparticle structures, nanoparticle shapes
are also equally important when matrix–filler interaction is considered in polymer
nanocomposites, which can be classified into three popular shapes, namely 1D
platelet-like nanoparticles such as montmorillonite (MMT) clays and graphene
nanoplatelet sheets, 2D tubular nanoparticles like HNTs and carbon nanotubes
(CNTs) and 3D spherical or near-spherical nanoparticles including NBCs, diamond
nanoparticles and nanosilica particles. In a nanocomposite system, the alteration of
nanoparticle shapes means that the contact areas inevitably vary between polymer
matrices and nanoparticles to effectively control the volume of interfacial regions
between them [8]. Most previous studies [9, 10] were based on theoretical or numerical modelling approaches like atomistic and coarse-grained molecular dynamic
(MD) simulations for evaluating matrix–filler bonding effect. Nonetheless, current
computational capability and environment may be mostly restricted to the context
of single- and two-particle systems by neglecting the effect of actual nanoparticle
structures and shapes that are induced in different material processing techniques
[11].
4.2 Nanoparticle Shape and Size
Morphological structures of as-received nanoparticles of Cloisite 30B clays, HNTs
and NBCs are illustrated in Fig. 4.1. All nanoparticle powders show high irregularities in size and material morphology. However, HNTs are most likely to possess
cylindrical shapes with transparent central areas running longitudinally along such
cylindrical structures, as illustrated in Fig. 4.1a, b. The outer diameters and lumen
diameters of HNTs, as typical tubular nanoparticles in hollow and open-end structures, were found to be in a range of 20–115 and 5–30 nm, respectively, while the
lengths of HNTs vary from 50 nm to 1.5 μm. On the other hand, morphological structures of Cloisite 30B clays were detected using an AFM tapping mode from diluted
clay suspension when deposited onto the mica substrate, as revealed in Fig. 4.1c, d. It
is evidently seen that Cloisite 30B clays possess platelet-like structures with average
4 PVA Bionanocomposite Films with Different Particle …
10 wt%, optical [3], mechanical [4], thermal [5], electronic [6] and antimicrobial [7]
properties can be remarkably enhanced in polymer nanocomposites, while some key
features of net polymer systems remain such as low density and high processibility
[2]. Such polymer nanocomposites have a wide range of applications in range of
aerospace engineering, automotive components and medical devices [1]. The effective reinforcing mechanism is based on a fundamental concept that the chain mobility
of polymeric molecules is restricted by rigid nanofillers according to matrix–particle
interfacial interactions in polymer nanocomposites [2, 8]. The specific areas associated with matrix–filler interactions are known as interfacial regions with completely
distinct properties from nanoparticles and polymer matrices alone. More importantly, the material performance of polymer nanocomposites primarily depends on
the volume of interfacial regions and properties [8] in relation to critical nanofiller
factors such as nanoparticle shapes and structures.
In addition to a major concern of nanoparticle structures, nanoparticle shapes
are also equally important when matrix–filler interaction is considered in polymer
nanocomposites, which can be classified into three popular shapes, namely 1D
platelet-like nanoparticles such as montmorillonite (MMT) clays and graphene
nanoplatelet sheets, 2D tubular nanoparticles like HNTs and carbon nanotubes
(CNTs) and 3D spherical or near-spherical nanoparticles including NBCs, diamond
nanoparticles and nanosilica particles. In a nanocomposite system, the alteration of
nanoparticle shapes means that the contact areas inevitably vary between polymer
matrices and nanoparticles to effectively control the volume of interfacial regions
between them [8]. Most previous studies [9, 10] were based on theoretical or numerical modelling approaches like atomistic and coarse-grained molecular dynamic
(MD) simulations for evaluating matrix–filler bonding effect. Nonetheless, current
computational capability and environment may be mostly restricted to the context
of single- and two-particle systems by neglecting the effect of actual nanoparticle
structures and shapes that are induced in different material processing techniques
[11].
4.2 Nanoparticle Shape and Size
Morphological structures of as-received nanoparticles of Cloisite 30B clays, HNTs
and NBCs are illustrated in Fig. 4.1. All nanoparticle powders show high irregularities in size and material morphology. However, HNTs are most likely to possess
cylindrical shapes with transparent central areas running longitudinally along such
cylindrical structures, as illustrated in Fig. 4.1a, b. The outer diameters and lumen
diameters of HNTs, as typical tubular nanoparticles in hollow and open-end structures, were found to be in a range of 20–115 and 5–30 nm, respectively, while the
lengths of HNTs vary from 50 nm to 1.5 μm. On the other hand, morphological structures of Cloisite 30B clays were detected using an AFM tapping mode from diluted
clay suspension when deposited onto the mica substrate, as revealed in Fig. 4.1c, d. It
is evidently seen that Cloisite 30B clays possess platelet-like structures with average