2
1 Introduction to PVA-Based Bionanocomposite Films
pollution. It has been reported that about 5.25 trillion plastic particles (weighing
269,000 tons) are floating on the sea [7]. such ubiquitous plastic particles in form
of micro- or nanosizes in the marine environment could result in the entanglement
of species by marine debris including marine mammals and other species in net
fragment litter [7].
Moreover, proposed solutions such as waste accumulation in landfill are unsatisfactory on the long term because of limited landfill sites in continuous urban development. In addition, the incineration of plastic wastes produces a large amount of
carbon dioxide and hazardous emission such as dioxins, resulting in the detrimental
effect on our ecosystems. On the other hand, recycling plastic wastes is often noneconomical with the availability of insufficient processing infrastructures while the
quality of recycled plastics is lower than that of virgin materials. In response to
these concerns, the development of biopolymers has become an increasingly high
priority for material scientists and engineers. Such polymers would not involve the
use of toxic gases in their manufacture, and thus can easily degrade in the environment. According to different manufacturing routes, biodegradable polymers can
be classified as (i) agro-polymers based on the biomass of agro-resources as raw
materials (e.g. starch and cellulose), (ii) polymers based on microbial production
(e.g. polyhydroxyalkanoates), (iii) polymers that are chemically synthesised using
biomass-based monomers (e.g. poly(lactic acid) (PLA)) and (iv) polymers that are
produced from the chemical synthesis of petroleum resources [4, 8]. Among those
categories, polyvinyl alcohol (PVA), as one of most popular water-soluble polymers, has practically gained considerable attention due to its favourable mechanical
properties, thermal resistance, excellent flexibility [9], recyclability and biotribological properties [10]. Furthermore, its biotechnological applications comprise tissue
engineering, drug delivery, articular cartilage and biosensors [11].
In recent years, the incorporation of nanofillers such as montmorillonite (MMT)
clays [12, 13], halloysite nanotubes (HNTs) [14–16], carbon nanotubes (CNTs) [17,
18], graphene sheets [19, 20], cellulose nanocrystals (CNCs) [21, 22], laponite [23]
and nanodiamond [24] into PVA matrices in newly developed nanocomposite systems
have be the major focus in order to significantly improve mechanical and thermal
properties, as well as biodegradability of PVA nanocomposites.
CNTs are considered as effective reinforcements widely used in polymer
nanocomposites. In addition to their high material cost, nanotoxicity is deemed as the
significant drawback of CNTs due of their accumulation in cytoplasm with resulting
ability to destroy human cells under certain inhalational conditions [25]. On the other
hand, graphene sheets have also experienced limited use owing to their tendency to
form agglomerates [26]. More recently, BCs, as newly used carbon-based particles,
are employed as effective reinforcements with unique ecofriendly and environmentally sustainable material features. Such BC particles are generally produced from
carbonised bamboo and bamboo residues at a typical temperature of 1000 °C under
nitrogen atmosphere [27], which results in the formation of significant amounts of
lengthwise and crosswise pores within BC structures [27, 28]. More impressively,
their volumetric porosity, mineral constituents and absorption efficiency are approximately 5, 8 and 10 times more than those of wood charcoals [27]. Besides, inner
1 Introduction to PVA-Based Bionanocomposite Films
pollution. It has been reported that about 5.25 trillion plastic particles (weighing
269,000 tons) are floating on the sea [7]. such ubiquitous plastic particles in form
of micro- or nanosizes in the marine environment could result in the entanglement
of species by marine debris including marine mammals and other species in net
fragment litter [7].
Moreover, proposed solutions such as waste accumulation in landfill are unsatisfactory on the long term because of limited landfill sites in continuous urban development. In addition, the incineration of plastic wastes produces a large amount of
carbon dioxide and hazardous emission such as dioxins, resulting in the detrimental
effect on our ecosystems. On the other hand, recycling plastic wastes is often noneconomical with the availability of insufficient processing infrastructures while the
quality of recycled plastics is lower than that of virgin materials. In response to
these concerns, the development of biopolymers has become an increasingly high
priority for material scientists and engineers. Such polymers would not involve the
use of toxic gases in their manufacture, and thus can easily degrade in the environment. According to different manufacturing routes, biodegradable polymers can
be classified as (i) agro-polymers based on the biomass of agro-resources as raw
materials (e.g. starch and cellulose), (ii) polymers based on microbial production
(e.g. polyhydroxyalkanoates), (iii) polymers that are chemically synthesised using
biomass-based monomers (e.g. poly(lactic acid) (PLA)) and (iv) polymers that are
produced from the chemical synthesis of petroleum resources [4, 8]. Among those
categories, polyvinyl alcohol (PVA), as one of most popular water-soluble polymers, has practically gained considerable attention due to its favourable mechanical
properties, thermal resistance, excellent flexibility [9], recyclability and biotribological properties [10]. Furthermore, its biotechnological applications comprise tissue
engineering, drug delivery, articular cartilage and biosensors [11].
In recent years, the incorporation of nanofillers such as montmorillonite (MMT)
clays [12, 13], halloysite nanotubes (HNTs) [14–16], carbon nanotubes (CNTs) [17,
18], graphene sheets [19, 20], cellulose nanocrystals (CNCs) [21, 22], laponite [23]
and nanodiamond [24] into PVA matrices in newly developed nanocomposite systems
have be the major focus in order to significantly improve mechanical and thermal
properties, as well as biodegradability of PVA nanocomposites.
CNTs are considered as effective reinforcements widely used in polymer
nanocomposites. In addition to their high material cost, nanotoxicity is deemed as the
significant drawback of CNTs due of their accumulation in cytoplasm with resulting
ability to destroy human cells under certain inhalational conditions [25]. On the other
hand, graphene sheets have also experienced limited use owing to their tendency to
form agglomerates [26]. More recently, BCs, as newly used carbon-based particles,
are employed as effective reinforcements with unique ecofriendly and environmentally sustainable material features. Such BC particles are generally produced from
carbonised bamboo and bamboo residues at a typical temperature of 1000 °C under
nitrogen atmosphere [27], which results in the formation of significant amounts of
lengthwise and crosswise pores within BC structures [27, 28]. More impressively,
their volumetric porosity, mineral constituents and absorption efficiency are approximately 5, 8 and 10 times more than those of wood charcoals [27]. Besides, inner