2.1 Materials
43
2.1.2.3 Halloysite Nanotubes (HNTs)
HNTs belong to the kaolin group of clay minerals with a chemical formula of
Al 2 Si 2 O 5 (OH) 4 ·nH 2 O [2]. In this work, HNTs were donated by Imerys Ceramics,
Auckland, New Zealand, with their material specification listed in Table 2.1.
2.2 Fabrication of PVA-Based Bionanocomposite Films
PVA/MBC bionanocomposite films were prepared by a solution casting method, as
shown in Fig. 2.2. Initially, 5 wt%/v PVA aqueous solution was prepared by dissolving
10 g PVA into 190 ml deionised water via vigorous magnetic stirring at 400 rpm and
90 °C for 3 h until PVA was completely dissolved to prepare a stock solution. MBC
aqueous suspension was obtained by using mechanical mixing in deionised water
with a rotor speed of 405 rpm at 40 °C for 2 h, which was followed by the ultrasonication (Model ELMA Ti–H–5) at 25 kHz and 40 °C with a power intensity of 70%
for 1 h. Subsequently, MBC contents of 0, 3, 5 and 10 wt% were obtained by adding
appropriate amounts of PVA. The MBC aqueous suspension was gradually added
in a dropwise manner into PVA solutions, simultaneously subjected to mechanical
mixing at 405 rpm and 40 °C for 2 h. Further, their mixtures were stirred at 400 rpm
and 90 °C for 1 h prior to subsequent sonication for 30 min to achieve uniform dispersion of MBCs. Finally, 20 ml prepared solution was cast on a glass petri dish and
allowed to dry in an air-circulating oven at 40 °C for 48 h. Afterwards, PVA/MBC
nanocomposite films were stored in a silica gel-containing desiccator before material testing and analysis. PVA/NBC bionanocomposites, PVA/HNT bionanocomposites and PVA/Cloisite 30B clay bionanocomposites were also subjected to the same
fabrication procedure in an identical processing condition.
2.3 Characterisation Techniques
The material performance of PVA bionanocomposite films and the effect of different
nanofiller contents and shapes on final bionanocomposite films are often evaluated
with various characterisation techniques. In this study, morphological structures,
mechanical and thermal properties, as well as nanomechanical features were holistically investigated, as shown in Fig. 2.3 and Table 2.2, which are explained in the
following subsections.
43
2.1.2.3 Halloysite Nanotubes (HNTs)
HNTs belong to the kaolin group of clay minerals with a chemical formula of
Al 2 Si 2 O 5 (OH) 4 ·nH 2 O [2]. In this work, HNTs were donated by Imerys Ceramics,
Auckland, New Zealand, with their material specification listed in Table 2.1.
2.2 Fabrication of PVA-Based Bionanocomposite Films
PVA/MBC bionanocomposite films were prepared by a solution casting method, as
shown in Fig. 2.2. Initially, 5 wt%/v PVA aqueous solution was prepared by dissolving
10 g PVA into 190 ml deionised water via vigorous magnetic stirring at 400 rpm and
90 °C for 3 h until PVA was completely dissolved to prepare a stock solution. MBC
aqueous suspension was obtained by using mechanical mixing in deionised water
with a rotor speed of 405 rpm at 40 °C for 2 h, which was followed by the ultrasonication (Model ELMA Ti–H–5) at 25 kHz and 40 °C with a power intensity of 70%
for 1 h. Subsequently, MBC contents of 0, 3, 5 and 10 wt% were obtained by adding
appropriate amounts of PVA. The MBC aqueous suspension was gradually added
in a dropwise manner into PVA solutions, simultaneously subjected to mechanical
mixing at 405 rpm and 40 °C for 2 h. Further, their mixtures were stirred at 400 rpm
and 90 °C for 1 h prior to subsequent sonication for 30 min to achieve uniform dispersion of MBCs. Finally, 20 ml prepared solution was cast on a glass petri dish and
allowed to dry in an air-circulating oven at 40 °C for 48 h. Afterwards, PVA/MBC
nanocomposite films were stored in a silica gel-containing desiccator before material testing and analysis. PVA/NBC bionanocomposites, PVA/HNT bionanocomposites and PVA/Cloisite 30B clay bionanocomposites were also subjected to the same
fabrication procedure in an identical processing condition.
2.3 Characterisation Techniques
The material performance of PVA bionanocomposite films and the effect of different
nanofiller contents and shapes on final bionanocomposite films are often evaluated
with various characterisation techniques. In this study, morphological structures,
mechanical and thermal properties, as well as nanomechanical features were holistically investigated, as shown in Fig. 2.3 and Table 2.2, which are explained in the
following subsections.