3
integrative research directions have been highlighted. In addition, for developing
plastic waste remediation technology, improved waste collection and segregation
methods are central.
1.2 Plastic Properties and Its Types
The term plastic is coined from the French word plastique which itself means the
ability to mold (Albus et al. 2006). A polymeric plastic is made from phenol and
formaldehyde, Bakelite discovered by Leo Baekeland in the year 1909, which was
the first completely synthetic material with numerous applications. Polyethylene
was accidentally discovered in the year 1898, not taken in much notice was rediscovered in 1933 by another accidental mixing of ethylene and benzaldehyde at high
temperature and pressure (Baker 2018). Now, plastics entered in the daily human
life, from the very initial use of cellulite material in place of today’s plastic. The
discovery and rediscovery of plastic has been continued with varying raw material
and conditions to produce more and more versatile material. This development of
material elements has been used for many applications from packing, construction,
and medical advancement (Andrady and Neal 2009; Saeedi et al. 2011). Basically,
plastics are polymer of high molecular weight, and stable carbon backbones make
them hydrophobic and nondegradable in nature. However, after polyethylene discovery, many polyolefins were developed and introduced in the market by varying
the arrangement of atoms and modifying or changing monomeric units in the chain
and various forms of plastic discovered.
Plastics have been classified on the basis of origin, molding ability, recyclability,
and monomers (Van Krevelen and Te Nijenhuis 2009; Nicholson 2017) (Fig. 1.1).
Plastics are classified as natural and synthetic on the basis of their origin, where it is
understandable that natural plastics are made up of natural raw materials (i.e., cellulose, lignin, silk, and protein) and synthetic ones are man-made besides from an
unnatural source (i.e., polyethylene, polyester, polystyrene, and polyvinyl chloride)
(Jabbar 2017). Another classification system is thermal or molding properties where
one is thermosetting (cannot be molded by heating) (i.e., melamine, phenol formaldehyde and polyurethane) and another is thermoplastic (molded after heating) (i.e.,
polyolefins, vinyl polymers and polycarbonates) that also defines molding ability
and recyclability. They are also classified based on the monomers: homopolymer
(chain of same monomers) (i.e., polyethylene, polypropylene, polystyrene, and
polyvinyl chloride) and copolymer (chains of two or more types of monomers) (i.e.,
polyethylene terephthalate, nylon, and polyurethane). The synthetic thermoplastics
were further classified based on their recyclability by coding them with numerical
values inside a closed triangular arrow symbolizing their recyclability (Society of
the Plastics Industry coding) [poly ethylene terephthalate (1), polyvinyl chloride
(3), high-density polyethylene (2), low density polyethylene (4), polypropylene (5),
polystyrene (6), polycarbonate/polyurethane (7)] (Halden 2010; Garcia and
Robertson 2017; Rahimi and García 2017) (Fig. 1.2).
1 Microbial Degradation of Plastics and Its Biotechnological Advancement
integrative research directions have been highlighted. In addition, for developing
plastic waste remediation technology, improved waste collection and segregation
methods are central.
1.2 Plastic Properties and Its Types
The term plastic is coined from the French word plastique which itself means the
ability to mold (Albus et al. 2006). A polymeric plastic is made from phenol and
formaldehyde, Bakelite discovered by Leo Baekeland in the year 1909, which was
the first completely synthetic material with numerous applications. Polyethylene
was accidentally discovered in the year 1898, not taken in much notice was rediscovered in 1933 by another accidental mixing of ethylene and benzaldehyde at high
temperature and pressure (Baker 2018). Now, plastics entered in the daily human
life, from the very initial use of cellulite material in place of today’s plastic. The
discovery and rediscovery of plastic has been continued with varying raw material
and conditions to produce more and more versatile material. This development of
material elements has been used for many applications from packing, construction,
and medical advancement (Andrady and Neal 2009; Saeedi et al. 2011). Basically,
plastics are polymer of high molecular weight, and stable carbon backbones make
them hydrophobic and nondegradable in nature. However, after polyethylene discovery, many polyolefins were developed and introduced in the market by varying
the arrangement of atoms and modifying or changing monomeric units in the chain
and various forms of plastic discovered.
Plastics have been classified on the basis of origin, molding ability, recyclability,
and monomers (Van Krevelen and Te Nijenhuis 2009; Nicholson 2017) (Fig. 1.1).
Plastics are classified as natural and synthetic on the basis of their origin, where it is
understandable that natural plastics are made up of natural raw materials (i.e., cellulose, lignin, silk, and protein) and synthetic ones are man-made besides from an
unnatural source (i.e., polyethylene, polyester, polystyrene, and polyvinyl chloride)
(Jabbar 2017). Another classification system is thermal or molding properties where
one is thermosetting (cannot be molded by heating) (i.e., melamine, phenol formaldehyde and polyurethane) and another is thermoplastic (molded after heating) (i.e.,
polyolefins, vinyl polymers and polycarbonates) that also defines molding ability
and recyclability. They are also classified based on the monomers: homopolymer
(chain of same monomers) (i.e., polyethylene, polypropylene, polystyrene, and
polyvinyl chloride) and copolymer (chains of two or more types of monomers) (i.e.,
polyethylene terephthalate, nylon, and polyurethane). The synthetic thermoplastics
were further classified based on their recyclability by coding them with numerical
values inside a closed triangular arrow symbolizing their recyclability (Society of
the Plastics Industry coding) [poly ethylene terephthalate (1), polyvinyl chloride
(3), high-density polyethylene (2), low density polyethylene (4), polypropylene (5),
polystyrene (6), polycarbonate/polyurethane (7)] (Halden 2010; Garcia and
Robertson 2017; Rahimi and García 2017) (Fig. 1.2).
1 Microbial Degradation of Plastics and Its Biotechnological Advancement