of used plastic have been made to be re-used especially for the used-plastics from
shopping. The challenge is in getting the family and community units to develop
collection centre with waste segregation in place especially when involving mixed
plastic wastes from various sources. A workable framework can be devised considering the social, economic and environmental benefits as a whole that can be
gained (Al Salem et al. 2009; Pruter 1987).
2.4.2 Mechanical Recycling
Mechanical recycling methods have been used to reduce the time in getting the
recycled fresh-products and the resources required which are the old plastics. The
three important steps involved are processing, granulating, and cutting. The homogeneous plastic wastes are used to produce the products with almost similar or
slighly lower in terms of durability and mechanical strength, than the original product. During cutting process, bigger plastics are broken down into smaller plastics
using a saw or shear. Strong blower is used to remove impurities from plastics. The
plastic drops are separated in a skimming container based on sizes and thickness.
Those plastics which consist of only one type of polymer are further ground. The
plastics are washed and dried as to the form required. In the synthesis process,
washing is done in specific cases with different chemicals for that special surface
characteristic of the plastic. With the appearance of colors, the whole batch is ready
to be marketed. Otherwise, the recycled plastics can turned into pellets and beads,
packed and sold (Putun et al. 2008). Mechanical recycling is a green but can
be expensive due to the high energy requirement for cleaning, transportation, and
raw material or product sorting (Panda et al. 2010).
The polyethylene terephthalate wastes have been converted into smaller particles,
washed several times with water, before being put into the centrifugal machine. The
waste products like dust are removed in several steps. During crushing, particle sizes
of 10–14 mm, and powdered forms of plastics are formed. Then, heating at the
prescribed conditions further remove all the pollutants. In the vibratory separator,
extra water is removed and a few modifiers and chemicals are added to get the
specific plastic properties. The recycled plastic materials are cooled in the air, and the
smaller particles are removed by using a sifter (Saikia and de Brito 2012).
2.4.3 Degradation of Thermoplastic Polyolefin and Additives
Generally, polyolefin cannot be decomposed by microorganisms as they are hydrophobic in nature, and their breakdown in the absence of water cannot take place. The
antioxidants introduced during the manufacturing prevent the plastics from being
broken down into smaller particles. Furthermore there are additives that could
further confer mechanical strength to some plastics. Those compounds which can
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Z. Tahir et al.
shopping. The challenge is in getting the family and community units to develop
collection centre with waste segregation in place especially when involving mixed
plastic wastes from various sources. A workable framework can be devised considering the social, economic and environmental benefits as a whole that can be
gained (Al Salem et al. 2009; Pruter 1987).
2.4.2 Mechanical Recycling
Mechanical recycling methods have been used to reduce the time in getting the
recycled fresh-products and the resources required which are the old plastics. The
three important steps involved are processing, granulating, and cutting. The homogeneous plastic wastes are used to produce the products with almost similar or
slighly lower in terms of durability and mechanical strength, than the original product. During cutting process, bigger plastics are broken down into smaller plastics
using a saw or shear. Strong blower is used to remove impurities from plastics. The
plastic drops are separated in a skimming container based on sizes and thickness.
Those plastics which consist of only one type of polymer are further ground. The
plastics are washed and dried as to the form required. In the synthesis process,
washing is done in specific cases with different chemicals for that special surface
characteristic of the plastic. With the appearance of colors, the whole batch is ready
to be marketed. Otherwise, the recycled plastics can turned into pellets and beads,
packed and sold (Putun et al. 2008). Mechanical recycling is a green but can
be expensive due to the high energy requirement for cleaning, transportation, and
raw material or product sorting (Panda et al. 2010).
The polyethylene terephthalate wastes have been converted into smaller particles,
washed several times with water, before being put into the centrifugal machine. The
waste products like dust are removed in several steps. During crushing, particle sizes
of 10–14 mm, and powdered forms of plastics are formed. Then, heating at the
prescribed conditions further remove all the pollutants. In the vibratory separator,
extra water is removed and a few modifiers and chemicals are added to get the
specific plastic properties. The recycled plastic materials are cooled in the air, and the
smaller particles are removed by using a sifter (Saikia and de Brito 2012).
2.4.3 Degradation of Thermoplastic Polyolefin and Additives
Generally, polyolefin cannot be decomposed by microorganisms as they are hydrophobic in nature, and their breakdown in the absence of water cannot take place. The
antioxidants introduced during the manufacturing prevent the plastics from being
broken down into smaller particles. Furthermore there are additives that could
further confer mechanical strength to some plastics. Those compounds which can
78
Z. Tahir et al.