6
1 Introduction to PVA-Based Bionanocomposite Films
Fig. 1.1 Chemical structures: a viny alcohol and b PVA [25]
chemical structures of PVA and viny alcohol are shown in Fig. 1.1. PVA has been
synthesised by several routes such as the polyaldol condensation of acetaldehyde
despite its little success until now [60]. In addition, the polymerisation of metal
compounds, followed by the saponification process, produces low-molecular-weight
PVA. However, the synthesis of PVA by the polymerisation of vinyl ester or ethers,
further subjected to the saponification or esterification, is regarded as the most popular
method [13, 60, 61]. In this technique, vinyl ester or other derivatives such as vinyl
mono and dichloroacetate are usually used as base materials for manufacturing PVA.
Moreover, PVA characteristics like molecular weight and residual content of acetyl
groups can be controlled by optimising processing parameters such as polymerisation
temperature, vinyl acetate/methoanol ratio and polymerisation conversion [62]. It has
been reported that the decrease in polymerisation temperature with an appropriate
proportion of methonal and conversion yields an increase in the molecular weight
of final PVA [62]. In addition, PVA should be free from monomeric vinyl acetate to
avoid the cosaponification [60]. The conversion process of PVAc to PVA is usually
carried out in the solution, suspension, or emulsion in the presence of alkaline or
1 Introduction to PVA-Based Bionanocomposite Films
Fig. 1.1 Chemical structures: a viny alcohol and b PVA [25]
chemical structures of PVA and viny alcohol are shown in Fig. 1.1. PVA has been
synthesised by several routes such as the polyaldol condensation of acetaldehyde
despite its little success until now [60]. In addition, the polymerisation of metal
compounds, followed by the saponification process, produces low-molecular-weight
PVA. However, the synthesis of PVA by the polymerisation of vinyl ester or ethers,
further subjected to the saponification or esterification, is regarded as the most popular
method [13, 60, 61]. In this technique, vinyl ester or other derivatives such as vinyl
mono and dichloroacetate are usually used as base materials for manufacturing PVA.
Moreover, PVA characteristics like molecular weight and residual content of acetyl
groups can be controlled by optimising processing parameters such as polymerisation
temperature, vinyl acetate/methoanol ratio and polymerisation conversion [62]. It has
been reported that the decrease in polymerisation temperature with an appropriate
proportion of methonal and conversion yields an increase in the molecular weight
of final PVA [62]. In addition, PVA should be free from monomeric vinyl acetate to
avoid the cosaponification [60]. The conversion process of PVAc to PVA is usually
carried out in the solution, suspension, or emulsion in the presence of alkaline or