CHEE 583 Plastic Recycling

8/12/2019 CHEE 583 Plastic Recycling

1/18

CHEE 583PLASTIC RECYCLING

Engr. Lina D. dela Cruz

Chemical Engineering DepartmentTechnological Institute of the

Philippines


2/18

Plastic recycling is the term given to the

processing of waste plastic which turns oldor scrap plastic in to a useable product

which can then re-enter the

manufacturing chain.


3/18


4/18

Plastic recyclingis the process of recovering

scrap or wasteplasticand reprocessing thematerial into useful products, sometimes

completely different in form from their

original state.
http://en.wiktionary.org/wiki/recoveryhttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Plastichttp://en.wiktionary.org/wiki/recovery


5/18

For instance, this could mean melting down

soft drinkbottles and then casting them asplastic chairs and tables. Typically a plastic

is not recycled into the same type of plastic,

and products made from recycled plastics are

often not recyclable.
http://en.wikipedia.org/wiki/Soft_drinkhttp://en.wikipedia.org/wiki/Soft_drink


6/18

Challenges

When compared to other materials like glass

and metal, plastic polymers require greaterprocessing (heat treating, thermal

depolymerization and monomer recycling) to

be recycled.


7/18

Due to the high molecular weight of their largepolymer chains, plastics have a low entropy of

mixing. A macro molecule interacts with itsenvironment along its entire length, so total energyinvolved in mixing it is large compared to that of anorganic molecule with a similar structure. Heating

alone is not enough to dissolve such a largemolecule, so plastics must often be of nearlyidentical composition to mix efficiently.


8/18

When different types of plastics are melted

together, they tend to phase-separate, like oiland water, and set in these layers.

The phase boundaries cause structural

weakness in the resulting material, meaning

that polymer blends are useful in only limited

applications.


9/18


10/18

Yet another barrier to removing large quantities of

plastic from the waste stream and landfills is the

fact that many common but small plastic items lack

the universal triangle recycling symbol and

accompanying number.

A perfect example is the billions of plastic utensilscommonly distributed at fast food restaurants or

sold for use at picnics.


11/18

5 STAGES OF RECYCLING

Stage One

Sorting the Plastic

Firstly the waste plastic needs to be collected by therecycling company, once the plastic arrives at the

recycling plant the first stage is sort the plastic in tothe specific types.

Plastic recycling is more complex than that of metalor glass recycling due to the many different types of

plastic and more importantly mixed plastic cannotbe used in manufacturing without delivering poorquality products.


12/18

Hence, that is why plastic recycling

companies need to be thorough when it

comes to sorting the waste plastic in to the

different forms prior to the next stage in the

recycling process


13/18


14/18

Stage Three- Shredding the

Plastic

The shredding stage is when the waste plastic

is taken and loaded on to conveyor belts or

directly in to huge hoppers that funnel the

clean scrap towards rotating metal teeth that

rip the plastic in to small pellets which are

bagged up afterwards ready for testing.


15/18

Stage FourIdentify andClassify the Plastic

Once the shredded plastic has been bagged it

is then chemically tested and labelled as to

its exact specification, this rGrade plastic can

be used as is by adding to a mix of virgin

plastic in a manufacturing run, alternatively

the rGrade plastic can be further recycled.


16/18

Stage Five - Extruding

This is the final stage in recycling plastic.

This involves melting the clean shreddedplastic and extruding in to the form of pellets

which then go on to manufacture the next lot

of plastic products.


17/18


18/18

Recycled products are becoming more

popular and are set to continue as oil

exploration moves to ever more hostile and

difficult to reach locations, which will of

course result in prices of products made from

oil will increase.

CHEE 583 Plastic Recycling

Documents

Transcript of CHEE 583 Plastic Recycling