Here we will see the classifications, Collection, Handling & Sorting, different methods of sorting of plastics
About Biodegradable polymers, how to use it and reuse it
1. POLYMER RECYCLING & USES
TRIPURA UNIVERSITY
(A CENTRAL UNIVERSITY)
PREPARED BY-
Abhijit Debnath
M. Tech, 1st Semester
Dept. Of Materials Science & Engineering
2. INTRODUCTION
Plastic is the general common term for a wide range of synthetic
or semi synthetic organic solid materials suitable for the
manufacture of industrial products.
Plastic is one of the few new chemical materials which pose
environmental problem. Polyethylene, polyvinyl chloride,
polystyrene, PET are largely used in the manufacture of plastics.
Plastics are typically polymers of high molecular weight, and
may contain other substances to improve performance and/or
reduce costs.
3. Polymers
Thermosets
Cannot be melted
Thermoplastics
Can be melted
Crystalline Amorphous
Semi- Crystalline
Polystyrene, polycarbonatePolypropylene, LDPE, HDPE
Polybutylene terephthalate (PBT), PET
CLASSIFICATION OF POLYMER
5. Plastics pollute beaches & oceans
plastic use has increased dramatically, resulting in a huge quantity of nearly
indestructible, lightweight material floating in the oceans
Plastic bags litter the landscape
if they are burnt, they infuse the air with toxic fumes.
Source: shutterstock.com
PLASTIC’S HARMFUL EFFECTS ON OUR ENVIRONMENT
6. Plastic bags kill animals
About 100,000 animals such as dolphins,
turtles whales, penguins are killed every
year due to plastic bags.
Plastic bags are non-biodegradable
The decomposition of plastic bags takes about 1000
years.
picture courtesy: www.onegreenplanet.org
7. PLASTIC’S EFFECT ON HUMAN LIFE
The major chemicals that go into the making of plastic are highly
toxic and pose serious threat to living beings of all species on
earth.
Some of the constituents of plastic such as benzene are known
to cause cancer.
Plastic resins themselves are flammable and have contributed
considerably to several accidents worldwide.
8. Percentage that can be recycled
About 7% of all household waste is
plastic.
Annually, 3 million tonnes of plastic
rubbish are produced.
57% of litter found on beaches is
plastic.
9. Why recycle plastic?
Conservation of non-renewable fossil fuels -
Plastic production uses 8% of the world's oil
production.
Reduced consumption of energy.
Reduced amounts of solid waste going to
landfill.
Reduced emissions of carbon-dioxide (CO2),
nitrogen-oxide (NO) and sulphur-dioxide (SO2).
10. How are polymers recycled?
1. Mechanical recycling of plastics refers to processes
which involve the melting, shredding or granulation of
waste plastics.
2. Plastics must be sorted prior to mechanical recycling.
3. At the moment most sorting for mechanical recycling
is done by trained staff who manually sort the plastics
into polymer type and/or colour.
4. Following sorting, the plastic is either melted down
directly and moulded into a new shape, or melted
down after being shredded into flakes and than
processed into granules called regranulate.
11. Source Reduction
Refers to a reduction in the amount of material
used in any application
The simplest methods to employ source
reduction are:
• To use fewer products that cause waste
• To choose size and types of products where-
by waste is minimized
• To reduce the material requirements of the
product (for manufacturer)
12. Recycling of Plastics
Reprocessing and refabrication of PCR
involves several steps;
Collection
Handling/sorting
Reclamation/sorting
End-use fabrication
13. Collection
Voluntary recycling by the consumer is the most
single factor in improving recycling of all materials
However, consumers do not sort their solid waste
but rather mix all materials together
For many plastics, the cost of virgin plastics is
about the same as the cost involve in recycling-
create problem in recycling process (different case
with recycling of aluminium cans)
14. Handling & Sorting
Involves conveying materials from the pickup point
(from consumer house) to the reclamation facility.
Sorting of materials is necessary (PET bottle, HDPE
waste, aluminium alloy, etc) or in broader material
groupings (all metals, all plastics, etc).
For the highest economy benefit, the HDPE and PET
and other recyclable plastics must be separated from the
plastics that are not to be recycled- thus considerable
labour is required to pick up the recyclables by hand.
15. Handling & Sorting
Some sorting can be done by machine, i.e. based
on certain characteristics (light absorption), various
plastic resins can be distinguished from the others.
Under certain condition, the mixture of several
plastic type can be recycled, called as mixed
recycled or comingled recycle.
To assist consumers and sorters, Society for
plastic Industry (SPI) introduced recycling
symbols.
16. Numbering system for plastic
recycling
Recycling No. Abbreviation Polymer Name
PETE or PET Polyethylene Terephthalate
HDPE High-Density Polyethylene
PVC or V Polyvinyl Chloride
LDPE Low-Density Polyethylene
PP Polypropylene
PS Polystyrene
OTHER
Other plastics, including acrylic,
polycarbonate, polylactic acid ,
nylon and fiberglass.
17. Polymer
Name
Uses
Polyethylene
Terephthalate
Recycled to produce polyester fibres, thermoformed sheet, strapping, soft
drink bottles, reinforcement for concrete.
High-Density
Polyethylene
Recycled to become various bottles, grocery bags, recycling bins, agricultural
pipe, base cups, car stops, playground equipment, and plastic lumber, flower
pot, toys
Polyvinyl
Chloride
Recycled to become pipe, fencing, and non-food bottles.
Low-Density
Polyethylene
Recycled to become plastic bags, various containers, dispensing bottles, wash
bottles, tubing, and various molded laboratory equipment.
Polypropylene Recycled into auto parts and industrial fibers.
Polystyrene
Recycled into a wide range of products including office accessories, cafeteria
trays, toys, video cassettes and cases, insulation board and styrofoam.
Uses of Different Polymers
18. Reclamation/Cleaning
After sorting, the plastics must be chopped into small
flakes or shredded for further processing.
Then the flakes are treated with solvents and washed
to remove residual contaminants (original content &
paper label).
The flakes are then sent to the fabricators to extrude
into pellets.
19. End Uses- Sorted PCR
The recycled material can be used in the same
applications or other applications.
However, PCR plastic cannot be used in medical
and food-contacting applications due to danger of
contamination and disease.
Thermoplastic- can be reheated and reprocessed
many times (with minor changes in resin
properties).
20. Degradation
Means that the plastic can break down into smaller
molecules by natural means, biological agent or by
sunlight.
In reality, some materials degrade very slowly.
Some applications require that the material do not
degrade, i.e. packaging material.
Some applications need degradable properties, i.e.
sutures in medical applications.
21. Incineration
Incineration or controlled burning is another option for disposing of large
percent of solid waste.
The most common purpose of burning is to generate electricity.
Energy content of various solid waste materials and conventional
fuels burned to generate electricity.
23. Obstacles of Recycling
Usage of various copolymer blends (i.e. PET) from different
manufacturers do not dissolve into one another when heated.
Instead, they tend to phase-separate, like oil and water.
Another barrier to recycling is the widespread use of dyes, fillers,
and other additives in plastics. The polymer is generally too viscous
to economically remove fillers, and would be damaged by many of
the processes that could cheaply remove the added dyes. Additives
are less widely used in beverage containers and plastic bags,
allowing them to be recycled more frequently.
24. Recycling plastic uses less water and energy resources than in producing
new plastics, and produces fewer greenhouse gases.
This is because the polymer chains become damaged or contaminated with food
or other types of plastic.
What is the effect of recycling plastics?
One problem with
recycling, however, is that
is reduces the strength
and versatility of the plastic
over time.
25. Biodegradable plastics are
increasingly being used in carrier
bags, bin bags and food packaging.
One of the problems with traditional plastics is that they do not break
down when thrown away.
Biodegradable plastics are plastics
that can be broken down. They are
converted into carbon dioxide, water
and minerals by micro-organisms.
Biodegradable plastics, such as polylactide, are plant-based polymers.
They are often made from starch that has been modified to become more
stable.
What are biodegradable plastics?
