7.7 Applications
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Agarose has thermoplastic properties as well as moderate water resistance (Makwana et al. 2018), and this has been explored in the production of packaging materials.
The limitations of agar for use in packaging materials are the brittleness at low moisture content, inferior mechanical properties compared to non-biodegradable thermoplastics such as low-density polyethylene and insufficient solvent resistance. These
properties of agar can be improved by combining with other materials and other
polymers in the form of composites and blends. Blends of two different polymers
can result in a material with superior properties than each individual polymer alone.
Similarly, a composite which is made up of a dispersed phase within a polymer
matrix can significantly improve the polymer in its neat form. The dispersed phase
could be made up of particles such as silver nanoparticles or fibers such as cellulose
nanofibers (Olatunji and Olsson 2015). An example of such enhancement of agar’s
properties using a combination of nanocomposite and blend is a blend of agar with
carboxymethyl cellulose (CMC) which is then dispersed with silver nanoparticles to
produce a packaging film with thermomechanical properties suitable for production
of packaging films. The introduction of silver nanoparticles improved antibacterial
properties and also the mechanical properties (Makwana et al. 2018). Nanocomposites can significantly boost the physical properties of polymers in nanocomposites;
however, their effect will be undermined if aggregation occurs. To prevent the aggregation of the silver nanoparticles within the agar-CMC nanocomposite, the silver
nanoparticles were contacted with montmorillonite clay to prevent their aggregation
within the polymer matrix. At 3 and 5% loading, silver nanoparticle and montmorillonite clay nanocomposite in agar-CMC blend resulted in 45 and 50% increase in
the tensile properties and increased the young modulus by 20 and 89%, respectively
(Makwana et al. 2018). Therefore, modified forms on agar can act as effective packaging materials with properties comparable to those of petroleum-based packaging
materials and thus serve as a more environmentally friendly packaging material.
Agar can also be cross-linked to improve its applicability as a biodegradable
plastic packaging. Cross-linking increases the water resistance, tensile and thermal
properties of agar. Cross-linkers such as diisocyanates can be used. Better cross-links
are achieved with aromatic diisocyanates than aliphatic ones. Non-cross-linked agar
has a water uptake value of 206%; when cross-linked with aromatic diisocyanate,
this is reduced to 33.6%. The tensile stress of cross-linked agar is 45.3 MPa, while
non-cross-linked agar has a tensile stress of 31.7 MPa (Sonker et al. 2018).
Recent patented technology of biodegradable thermoplastic packaging material
incorporates agar as a modifying agent. One of the requirements for packaging materials is the ability to be heat processed. They are therefore required to have thermoplastic characteristics. This allows for large-scale production using the conventional
continuous plastic processing techniques such as blown film extrusion. This contributes to reducing the cost of production of biodegradable plastics and also requiring less technological transition when the feed is changed from non-degradable to
biodegradable plastics. Biodegradable thermoplastic is a mixture of PLA and mTPS
(polylactic acid and modified thermoplastic starch). The mTPS comprises of agar,
epoxide and gum arabic. For example, formulation of such thermoplastic starch
163
Agarose has thermoplastic properties as well as moderate water resistance (Makwana et al. 2018), and this has been explored in the production of packaging materials.
The limitations of agar for use in packaging materials are the brittleness at low moisture content, inferior mechanical properties compared to non-biodegradable thermoplastics such as low-density polyethylene and insufficient solvent resistance. These
properties of agar can be improved by combining with other materials and other
polymers in the form of composites and blends. Blends of two different polymers
can result in a material with superior properties than each individual polymer alone.
Similarly, a composite which is made up of a dispersed phase within a polymer
matrix can significantly improve the polymer in its neat form. The dispersed phase
could be made up of particles such as silver nanoparticles or fibers such as cellulose
nanofibers (Olatunji and Olsson 2015). An example of such enhancement of agar’s
properties using a combination of nanocomposite and blend is a blend of agar with
carboxymethyl cellulose (CMC) which is then dispersed with silver nanoparticles to
produce a packaging film with thermomechanical properties suitable for production
of packaging films. The introduction of silver nanoparticles improved antibacterial
properties and also the mechanical properties (Makwana et al. 2018). Nanocomposites can significantly boost the physical properties of polymers in nanocomposites;
however, their effect will be undermined if aggregation occurs. To prevent the aggregation of the silver nanoparticles within the agar-CMC nanocomposite, the silver
nanoparticles were contacted with montmorillonite clay to prevent their aggregation
within the polymer matrix. At 3 and 5% loading, silver nanoparticle and montmorillonite clay nanocomposite in agar-CMC blend resulted in 45 and 50% increase in
the tensile properties and increased the young modulus by 20 and 89%, respectively
(Makwana et al. 2018). Therefore, modified forms on agar can act as effective packaging materials with properties comparable to those of petroleum-based packaging
materials and thus serve as a more environmentally friendly packaging material.
Agar can also be cross-linked to improve its applicability as a biodegradable
plastic packaging. Cross-linking increases the water resistance, tensile and thermal
properties of agar. Cross-linkers such as diisocyanates can be used. Better cross-links
are achieved with aromatic diisocyanates than aliphatic ones. Non-cross-linked agar
has a water uptake value of 206%; when cross-linked with aromatic diisocyanate,
this is reduced to 33.6%. The tensile stress of cross-linked agar is 45.3 MPa, while
non-cross-linked agar has a tensile stress of 31.7 MPa (Sonker et al. 2018).
Recent patented technology of biodegradable thermoplastic packaging material
incorporates agar as a modifying agent. One of the requirements for packaging materials is the ability to be heat processed. They are therefore required to have thermoplastic characteristics. This allows for large-scale production using the conventional
continuous plastic processing techniques such as blown film extrusion. This contributes to reducing the cost of production of biodegradable plastics and also requiring less technological transition when the feed is changed from non-degradable to
biodegradable plastics. Biodegradable thermoplastic is a mixture of PLA and mTPS
(polylactic acid and modified thermoplastic starch). The mTPS comprises of agar,
epoxide and gum arabic. For example, formulation of such thermoplastic starch