9.2 Definition and Classification of Plastics

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properties. Plastics are economically beneficial compared to other materials and

can be made in both opaque and translucent forms.

9.2.2

Classification

9.2.2.1

Based on Biodegradability

Biodegradable plastics are those plastics that are decomposed by the surrounding

environment after a period of time. The biodegradation of plastics can be accom-

plished by allowing the molecular structure of plastic films to be metabolized by

microorganisms in the atmosphere to produce a material that is inert and less toxic

to humans. They may come in the form of either bioplastics or petroleum-based

plastic products. Bioplastics are plastics made from recycled raw materials.

Biodegradability and microbial assimilation are the basis for the use of bio- and

fossil-based polymers in biodegradable plastics. Biodegradation process includes

enzymatic and non-enzymatic hydrolysis. Depending on the presence or absence of

oxygen, biodegradation results in the production of H2O, biomass, energy, CO2, and

methane [5].

Bio-based degradable plastics can be derived from renewable sources. From

an ecological point of view, biodegradable polymers are advantageous in some

commercial processes due to their ability to be degraded biologically. Cellulose,

starch, and many more starch-based degradable plastics such as co-polymers

are consumed directly by microorganisms. Several microorganisms such as

Aspergillus fumigatus, Variovorax paradoxus, Comamonas sp., Acidovorax facilis,

and Paucimonas lemoignei can be isolated from the environment such as soil. These

microorganisms can degrade the bio-based polymers both under both aerobic and

anaerobic conditions [6]. Biodegradable fossil-based plastics are used for a variety

of purposes, particularly for packaging purposes (Figure 9.1).

Biodegradable

Bio-based

Fossil-based

Starch-based

polymers

PLA

PHA

PBS

PES

PEA

PBSA

PCL

PVOH

Cellulose-based

polymers

Figure 9.1

Classification of plastics (based on biodegradability).