2. Plastic waste A Survey
• 3 million tonnes of waste plastic are produced a year.
• 1 tonne = 20,000 plastic bottles
• 7% of this is recycled at present (2015)
• An estimated 9.2 billion plastic bottles are disposed of each year
• 200,000 tonnes of plastic rubbish is being sent 8,000 miles to China
each year for recycling.
3. Why Recycle
• Question arises about what to do with plastic waste
• Waste accumulation has been a problem throughout history
• Growth in technology requires new materials
• Most consumer waste end up in landfill.
4. Definition
• Plastics -> are commercial materials made from synthetic polymers
• 2 types of polymers
-Thermoplastic polymers
*Structured linearly, Heat softened
-Thermoset polymers
*Formed with irreversible cross-linkages of covalent bonds, not heat softened
7. Types of Plastics
● There are seven different types of plastics that are each identified
by an identification number describing chemical makeup
8. 1. PETE- Polyethylene Terephthalate
● The brand name is Dacron
● It is a thermoplastic that is used in synthetic fibers such as:
-Beverage, food and other liquid containers -Thermoforming applications
-Engineering resins often in combination with glass fiber
● Because PETE is an excellent water and moisture barrier material, plastic bottles made from
PETE are widely used for soft drinks
● The majority of the world's PETE production is for synthetic fibers (more than 60%), with bottle
production accounting for around 30% of global demand
● This form of plastic is one of the most commonly recycled of the seven types
● In terms of textile applications, PETE is referred to by its common name, polyester. The acronym
"PETE" is generally used in relation to packaging.
9. PET consists of polymerized units of the
monomer ethylene terephthalate, with
repeating C10H8O4units.
This is a short piece of the PET polymer chain
10. 2. HDPE- High-density Polyethylene
1. HDPE is considered one of the safer plastics and is easily recycled.
● It is also stronger than standard Polyethylene, good barrier from moisture, and stays
solid at room temperature.
2. One other bonus is HDPE doesn’t leak any toxic chemicals into the soil or water.
3. This particular Plastic is known for its strength to density ratio.
4.Like most plastics it is made from petroleum.
Since this material can be remolded by subsequent melting and shaping, it is
classified as a polyethylene thermoplastic
12. 3. Vinyl
• Synthetic man-made material made from ethylene and chlorine
• Both the substances are combined to form Polyvinyl Chloride (PVC) resin
• It is the third-most widely produced plastic
• Low cost material to produce, very durable, resistant to moisture
• Used in construction because it is more effective than traditional materials
such as copper, iron or wood in pipe and profile applications
• It is also used in clothing and upholstery, electrical cable insulation, inflatable
products and many applications in which it replaces rubber when plasticizers
are added to it to make it softer and more flexible
• Easily recycled, and more environmentally friendly since 57% of vinyl is made
from common salt which is a renewable natural resource
13. About 80% of production involves suspension
polymerization. Emulsion polymerization
accounts for about 12% and bulk
polymerization accounts for 8%.
A strand of the Polyvinyl chloride chain
14. 4. LDPE- Low Density Polyethylene
• Thermoplastic made from monomer ethylene
• Started being produced in 1933
• Used in trays, caps/thin lids, six pack rings,plastic wraps, playground
slides.
• It can be withstand temperatures of 80 degrees celsius
• Its a very tough plastic but is breakable.
• Unlike PVC, LDPE is not regarded as a “bad plastic”
15.
16. 5. PP- Polypropylene
• Polypropylene is a plastic polymer with the chemical formula C3H6
• Another thermoplastic polymer that is known for being rugged and quite
resistant to solvents, bases, and acids
• Has a very high melting point of 320 degrees Fahrenheit making it
dishwasher safe
• Also very easy to add dyes to this type of plastic
• In 2008, the global market for polypropylene had a volume of 45.1
million metric tons, which led to a turnover of about $65 billion
17.
18. 6. PS- Polystyrene
• It is a synthetic aromatic polymer made from the monomer styrene, a liquid petrochemical
• Can be rigid or foamed; General purpose polystyrene is clear, hard and brittle
It is highly flammable
• It is very slow to biodegrade which is controversial because it is often abundant as a form of
litter in the outdoor environment, specifically along shores and waterways especially in its foam
form
• One of the most widely used plastics, the scale of its production is several billion kilograms per
year
• It’s uses include protective packaging (such as packing peanuts and CD and DVD cases),
containers, lids, bottles, trays, tumblers, and disposable cutlery
• Most polystyrene products are currently not recycled due to the lack of incentive to invest in the
compactors and logistical systems required. Due to the low density of polystyrene foam, it is not
economical to collect
• Foam scrap can be turned into clothes hangers, park benches, flower pots, toys, rulers, stapler
bodies, seedling containers, picture frames, and architectural molding from recycled PS
19. Polystyrene results when styrene monomers interconnect. In the
polymerization, the carbon-carbon pi bond (in the vinyl group) is broken and a
new carbon-carbon single (sigma) bond is formed, attaching another styrene
monomer to the chain.
20. 7. Other- Mixed Plastics
• Generally a wild card marking plastics that don’t fall within the other six categories
• Include polycarbonate bottles, which are understood by scientists to negatively affect human
hormones by leaching bisphenol-A into hot beverages
• Polycarbonate baby bottles are losing favor with the public, and retailers including are starting to
sell more BPA-free bottles
• Some examples of these plastics include:
o Silicone-Heat resistant material used mainly as a sealant but also used for high temperature
cooking utensils
o Furan- Resin based on Furfural Alcohol used in foundry sands and biologically derived
composites.
o Polyimide - A High temperature plastic used in materials such as Kapton tape
21.
22. Advantages of Recycling Plastic
• Waste reduction
• Conservation of energy
• Save money
• Create new jobs
• Generate revenues
• Reduced Oil Consumption-On average, 1 ton of recycled plastic saves 16.3
barrels of oil.
23. Advantages of Recycling Plastic
• Reducing Waste- Plastics break down slowly in a landfill. However, in the
ocean, for example - they can break down more quickly, but they still take
a long time to biodegrade; depending on the type of plastic it could be a
century or even more!
• Saving Energy- Recycling plastic still uses energy, but it usually requires
less energy than making fresh plastic. Recycling 1 ton of plastic saves the
equivalent of 5,774 kilowatt-hours of electric energy.
24. Types & Uses of Recycled plastic
two types of plastic ,
• polyethylene terephthalate (No.1) PET and
• high-density polyethylene (No.2), HDPE are recycled at most locations.
• Recycled PET and HDPE can be used to make new bottles, polyester fibers
for use in clothing, car parts and plastic lumber, among other products.
25. Disadvantages of Recycling Plastic
• Plastic resin, which is part of the manufacturing and recycling process, and
comes from petroleum, can get into foods stored in recycled plastic containers.
• Because of the potential health threats recycled plastic poses, much plastic
recycling is actually down cycling. This means that the plastic actually becomes
a different, less useful product.
• The cost associated with processing plastic categories 3-7 compared with the
return available from a secondary market drives many municipal recycling
programs to deny these items.
26. Problems with recycling plastics
• PET and PVC have many problems with cross contamination as
the two polymers appear very similar to the naked eye and
share the same specific gravity so cannot be separated by
conventional float-sink techniques used in the plastic recycling
industry.
• The correct separation of plastics is extremely important. Just
one PVC bottle in a batch of 10,000 PET bottles can ruin the
entire melt!
27. Recycling Of Polymers: The Reality
• Because of the
problems
outlined on the
previous slides,
the contribution
of recycling to
current plastic
consumption is
small.
Plasticproduction
(millionsoftonnes/year)
29. A different viewpoint...
• It takes one day to collect a kilo of thin
plastic bags from a tip by hand
• For one kilo, the rag picker typically
earns R1.5 in India
• Some cities in India are banning the use
of thin plastic bags
30. What Can WE Do?
•Some easy ways to reduce plastic waste include:
• Avoid using plastic straws, or purchase a stainless steel/ glass reusable one
• Use reusable bags at the grocery store, preferably cotton ones
• Buy boxes not bottles (laundry detergent, dish soap, etc.)
• Buy in bulk- the less plastic you purchase, the less you are throwing away
• Reuse plastic containers
• Reuse water bottles & caps
• Do not use plastic forks, spoons, etc.
