132
5 3D Interphase of PVA Bionanocomposite Films
Fig. 5.12 V interphase /V nanofillers as a function of V nanofillers for PVA/NBC bionanocomposites,
PVA/Cloisite 30B clay bionanocomposites and PVA/HNT bionanocomposites
5.2.4 Particle Debonding
When NBC loading increases up to 5 wt%, interparticle spacing appears to be smaller,
and NBCs tend to be interconnected with neighbouring particles side by side, illustrated in Fig. 5.13a, in which contact-free particles are clearly seen on some sides
within PVA matrices. Furthermore, a joint particle-to-particle formation may induce
the phase separation leading to scattered load transfer from PVA matrices to NBCs,
as evidenced by the particle overlap of NBCs in Fig. 5.13b. At the NBC loading of
10 wt%, NBC aggregation becomes manifested with a clear sign of large stacked-up
NBC agglomerates, displayed in Fig. 5.13c. As such, the particle-to-particle separation occurs more evidently with resulting weak interfacial bonding. Figure 5.13d
reveals the modulus-variation mapping on the surface cross section of a line scan (i.e.
the line between two ovals A 23 B 23 in Fig. 5.13c), which highlights two narrow zones
with a sharp decline in elastic modulus. In addition to particle dimensions, particle
dispersion and distribution patterns in polymer matrices are the other key factors
in controlling interfacial bonding between NBCs and PVA matrices in PVA/NBC
bionanocomposites. When excessive amounts of NBCs are dispersed within PVA
matrices, NBCs tend to agglomerate owing to their weak van der Waals interactions.
Additionally, increasing the particle loading inevitably decreases the interparticle
spacing, and thus hinders good particle dispersion [19]. Blighe et al. [20] reported
that the interparticle spacing was determined to be 6 nm in PVA nanocomposites
reinforced with 10 vol% single-walled CNTs (SWNTs) leading to typical particle
aggregation. As a result, a slippage phenomenon of stacked NBCs under mechanical loading gives rise to a less effective enhancement level for mechanical properties of nanocomposites. Moreover, particle agglomeration becomes apparent at
5 3D Interphase of PVA Bionanocomposite Films
Fig. 5.12 V interphase /V nanofillers as a function of V nanofillers for PVA/NBC bionanocomposites,
PVA/Cloisite 30B clay bionanocomposites and PVA/HNT bionanocomposites
5.2.4 Particle Debonding
When NBC loading increases up to 5 wt%, interparticle spacing appears to be smaller,
and NBCs tend to be interconnected with neighbouring particles side by side, illustrated in Fig. 5.13a, in which contact-free particles are clearly seen on some sides
within PVA matrices. Furthermore, a joint particle-to-particle formation may induce
the phase separation leading to scattered load transfer from PVA matrices to NBCs,
as evidenced by the particle overlap of NBCs in Fig. 5.13b. At the NBC loading of
10 wt%, NBC aggregation becomes manifested with a clear sign of large stacked-up
NBC agglomerates, displayed in Fig. 5.13c. As such, the particle-to-particle separation occurs more evidently with resulting weak interfacial bonding. Figure 5.13d
reveals the modulus-variation mapping on the surface cross section of a line scan (i.e.
the line between two ovals A 23 B 23 in Fig. 5.13c), which highlights two narrow zones
with a sharp decline in elastic modulus. In addition to particle dimensions, particle
dispersion and distribution patterns in polymer matrices are the other key factors
in controlling interfacial bonding between NBCs and PVA matrices in PVA/NBC
bionanocomposites. When excessive amounts of NBCs are dispersed within PVA
matrices, NBCs tend to agglomerate owing to their weak van der Waals interactions.
Additionally, increasing the particle loading inevitably decreases the interparticle
spacing, and thus hinders good particle dispersion [19]. Blighe et al. [20] reported
that the interparticle spacing was determined to be 6 nm in PVA nanocomposites
reinforced with 10 vol% single-walled CNTs (SWNTs) leading to typical particle
aggregation. As a result, a slippage phenomenon of stacked NBCs under mechanical loading gives rise to a less effective enhancement level for mechanical properties of nanocomposites. Moreover, particle agglomeration becomes apparent at