polymerization generates more water, where its presence may degrade the formed
polymer chain. By adding hydroxylic compounds, it is possible to control the
molecular weight of PLA, and PLAs with high molecular weight are certified as
GRAS (generally regarded as safe) by US FDA. It is an odorless, colorless, glossy,
stiff, low-toxicity polymer, suitable for direct food contact, and this biodegradable
polyester has highest melting temperatures, around 160–190
C [39].
The PLAs can structurally be classified into three types, namely, poly(D,L-lactide)
(PDLLA), poly(D-lactide) (PDLA), and poly(L-lactide) (PLLA) [40]. Among these,
PDLLA is fully amorphous, where the others PDLA and PLLA are semicrystalline.
Poly(D,L-lactide) with 90% L-lactide has been widely used for producing packaging
materials [41].
PLA is having performance similar to that of PET, so it is feasible to use PLA as a
potential substituent for PET in products like pouches, films and bottles, etc.
Because of its brittle nature, less elongation (<10%) at break, deprived gas barrier
properties, and high modulus and hydrophilic character, primarily its application has
been limited to thermoformed packaging [42]. As PLAs have low melt strength, to
process them into extruded sheets, foam and films’ higher melt strength is
required [43].
The PLA has better thermal properties when compared with other biopolymers
like poly(ε-caprolactone) (PCL), PHA, and polyethylene glycol (PEG). The PLA has
long crystallization rate, as it takes more period of time to form helical packing
structure. The PLA needs to be modified and blended with further biodegradable
polymers to use it for a wide variety of packaging applications. Conventional
techniques such as blow molding, injection molding, film extrusion, fiber spinning,
and thermoforming can be used for processing the blended PLAs [44]. The PLA
majorly can be used for producing disposable tableware and especially for packaging
foods having short shelf life like juices, yogurt, vegetables and fruits, etc.
For enhancing the properties like ductility and to accelerate crystallization, the
PLAs are needed to be blended with fillers or other additives to form PLA composite
films. So far many materials like nanoclays [45], plasticizers [46], starch [47], and
carbon nanotubes [48] were blended in making PLA matrix. The significant
improvements in thermal and mechanical properties were achieved when
2-methacryloyloxyethyl isocyanate (MOI) was blended with PLA [49]. The produced PLA-MOI, when compared with pure PLA, had 20 times higher percentage of
elongation. Jiang and Zhang [50] blended PLA with other bioplastics like PBS,
PHA, PCL, thermoplastic starch, and PBAT and achieved improved toughness and
ductility.
In a recent study carried out by Bandera et al. [51], a latex-coated paper which is
suitable for food packaging has been prepared by blending PLA with montmorillonite, surfactants, plasticizers, water, and chloroform via emulsion/solvent evaporation method. Improved water vapor transmission rate (up to 85%) was achieved in
coated papers and the latex material is nontoxic, so it can securely be used for food
packaging applications.
The properties of PLA may differ considerably from amorphous to semicrystalline based on D-lactide/L-lactide enantiomers ratio. In PLA the amorphous one,
Recent Developments in Food-Based Bioplastics Production
115
polymer chain. By adding hydroxylic compounds, it is possible to control the
molecular weight of PLA, and PLAs with high molecular weight are certified as
GRAS (generally regarded as safe) by US FDA. It is an odorless, colorless, glossy,
stiff, low-toxicity polymer, suitable for direct food contact, and this biodegradable
polyester has highest melting temperatures, around 160–190
C [39].
The PLAs can structurally be classified into three types, namely, poly(D,L-lactide)
(PDLLA), poly(D-lactide) (PDLA), and poly(L-lactide) (PLLA) [40]. Among these,
PDLLA is fully amorphous, where the others PDLA and PLLA are semicrystalline.
Poly(D,L-lactide) with 90% L-lactide has been widely used for producing packaging
materials [41].
PLA is having performance similar to that of PET, so it is feasible to use PLA as a
potential substituent for PET in products like pouches, films and bottles, etc.
Because of its brittle nature, less elongation (<10%) at break, deprived gas barrier
properties, and high modulus and hydrophilic character, primarily its application has
been limited to thermoformed packaging [42]. As PLAs have low melt strength, to
process them into extruded sheets, foam and films’ higher melt strength is
required [43].
The PLA has better thermal properties when compared with other biopolymers
like poly(ε-caprolactone) (PCL), PHA, and polyethylene glycol (PEG). The PLA has
long crystallization rate, as it takes more period of time to form helical packing
structure. The PLA needs to be modified and blended with further biodegradable
polymers to use it for a wide variety of packaging applications. Conventional
techniques such as blow molding, injection molding, film extrusion, fiber spinning,
and thermoforming can be used for processing the blended PLAs [44]. The PLA
majorly can be used for producing disposable tableware and especially for packaging
foods having short shelf life like juices, yogurt, vegetables and fruits, etc.
For enhancing the properties like ductility and to accelerate crystallization, the
PLAs are needed to be blended with fillers or other additives to form PLA composite
films. So far many materials like nanoclays [45], plasticizers [46], starch [47], and
carbon nanotubes [48] were blended in making PLA matrix. The significant
improvements in thermal and mechanical properties were achieved when
2-methacryloyloxyethyl isocyanate (MOI) was blended with PLA [49]. The produced PLA-MOI, when compared with pure PLA, had 20 times higher percentage of
elongation. Jiang and Zhang [50] blended PLA with other bioplastics like PBS,
PHA, PCL, thermoplastic starch, and PBAT and achieved improved toughness and
ductility.
In a recent study carried out by Bandera et al. [51], a latex-coated paper which is
suitable for food packaging has been prepared by blending PLA with montmorillonite, surfactants, plasticizers, water, and chloroform via emulsion/solvent evaporation method. Improved water vapor transmission rate (up to 85%) was achieved in
coated papers and the latex material is nontoxic, so it can securely be used for food
packaging applications.
The properties of PLA may differ considerably from amorphous to semicrystalline based on D-lactide/L-lactide enantiomers ratio. In PLA the amorphous one,
Recent Developments in Food-Based Bioplastics Production
115