Page 185 - Materials Chemistry, Second Edition

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Sustainable Industrial Design and Waste Management
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Plastic waste

Washing process

Sorting and
recycling

Agglomeration Shredding

Pelletizing

Injection Film/ Hose/
molding blowing extrusion
machine machine machine

FIGURE 5.11 Plastic recycling process flow diagram

goes back into the bottle market. China is currently using it for the manu-
facture of fiber optics (Connecticut Metal Industries, 2005).
Some common end uses for recycled HDPE are plastic pipes, lumber,
flower pots, and trash cans, or it is reformed into non-food application bot-
tles. Some end uses for recycled LDPE are plastic trash bags and grocery
sacks, plastic tubing, agricultural film, and plastic lumber.
To recycle plastics there are mainly three stages needed. The initial stage
is where the wastes are collected, sorted, separated, and cleaned; this stage is
mainly labor intensive requiring little capital investment and relatively no
technical skills. The second stage is where the collected wastes are being pre-
pared for reprocessing: in this stage, the wastes are reduced in size by undergo-
ing cutting, shredding, and agglomeration. The final stage is the reprocessing
stage, where mixing, extrusion, blowing, injection, and product manufacturing
takes place (Lardinos and van de Klundert, 1995) as shown in Figure 5.11.

Collection, sorting, separation, and cleaning stage
The first step in the initial stage is collection, which is usually carried out in
developing countries by the informal sector and small individual enterprises