The World of Polymers and PlasticsThe World of Polymers and Plastics

Why are plastics important?

What happens to recycled plastics and polymers?

What are plastics made from?

And the most important question of all -

paper or plastic?paper or plastic?

What do you think of when you hear the word “plastic”?What do you think of when you hear the word “plastic”?Rayon

Nylon

Lycra

polyurethane

Teflon

Styrofoam

Saran

Plastics are found Plastics are found everywhereeverywhere

Except for our food, air, and water almost every ordinary thing that we come in

contact with contains some sort of plastic in, on, or around it.

Plastics come in an amazing variety of colors, shapes, types, and textures

Plastics have found applications in nearly everything that we usehttp://www.youtube.com/watch?v=FJAHuhFptFohttp://www.freesciencenews.org/FreeTeacherVideos/

Natural polymers include such things as cellulose, starch, tar and shellac, tortoise shell and horns, as well as tree saps that produce amber and latex.

These polymers were processed with heat and pressure into useful articles like hair ornaments and jewelry.

The fractionation of crude oil produces the raw material used for the production of synthetic polymers.

Polymers have been with us since the beginning of timePolymers have been with us since the beginning of time

Plastics are PolymersPlastics are Polymers

Polymers are large molecules made up of long chains of monomers bonded together.

Monomers (from mono meaning “one” and meros meaning “unit”) are the small molecules used to synthesize the polymer chain, like a strand of paper clips.

What is a polymer?What is a polymer?

All plastics are polymers formed All plastics are polymers formed from chains of smaller moleculesfrom chains of smaller molecules

Polymers can be formed from the same type of monomer or from a combination of monomers

A representation of a polymer made of two different types of monomers

A representation of a monomer

A representation of a polymer made of one type of monomer

Polymers can be classified based Polymers can be classified based on the structures of their on the structures of their

monomersmonomers

HomopolymersHomopolymers consist of chains in which every monomer is identical

CopolymersCopolymers (or heteropolymers) are composed of chains with two or more different types of monomers

Polymers are called addition polymersaddition polymers when each monomer is added sequentially to the growing chain without any losses

Condensation polymersCondensation polymers are formed when each monomer combines with the loss of a small molecule (such as water)

Polymers can also be classified based Polymers can also be classified based on the type of reaction that is used to on the type of reaction that is used to

create themcreate them

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Addition polymerization Addition polymerization is the process of linking is the process of linking small molecules together to form chainssmall molecules together to form chains

ethylene

polyethylene

© 2003 John Wiley and Sons Publishers

Cellulose is a natural condensation polymerCellulose is a natural condensation polymer

Cellulose is formed by condensing glucose molecules and releasing molecules of water

Cellulose is the major component

of wood, paper and cotton

Today there are over 60,000 synthetic polymersToday there are over 60,000 synthetic polymers Three of the six most common polymers are:

What makes one polymer different from another?What makes one polymer different from another?

The other three of the “Big Six” are:

Separating plastics of different densities with a mixture of isopropyl alcohol (rubbing alcohol) and water.

The more dense plastics sink; the less dense plastics float.

Plastics have a wide range of Plastics have a wide range of propertiesproperties

The properties of plastics

depend on their molecular structures

Polymer PropertiesPolymer Properties

ThermoplasticsThermoplastics – polymers that soften when heated but become firm when cooled (examples: water bottles, compact discs)

Thermosetting plasticsThermosetting plastics – soft enough to be molded but become firm when heated (examples: plastic pipes, car parts)

ElastomersElastomers – polymers that stretch easily but return to their original shape (example: rubber)

Some applications of different types of plasticsSome applications of different types of plastics

Stretching or “necking” a plastic bagStretching or “necking” a plastic bag

The molecular rearrangement that occurs as PE is stretched

Pulling on a piece of PE

Why does the plastic stay distorted after it is pulled?Because the Because the molecular structure molecular structure is changed !is changed !

Branching alters the physical properties of PEBranching alters the physical properties of PE

Low density PE (LDPE) soft, stretchy, not very strong

High density PE (HDPE) greater rigidity and strength

linear PE branched PE

The conditions under which a The conditions under which a polymer is formed can change its polymer is formed can change its properties, even if the molecular properties, even if the molecular

formula is the sameformula is the same

Disorganized polymeric strands of low-density polyethylene.

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Polymeric strands of high-density polyethylene with regions of crystallinity.

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Different properties dictate different usesDifferent properties dictate different uses

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PET – a polyester copolymerPET – a polyester copolymer

PET consists of alternative monomers of ethylene glycol and terephthalic acid

Food storage bags made of poly(ethylene terephthalate) PET.

© 2003 John Wiley and Sons Publishers

© 2003 John Wiley and Sons Publishers

Polystyrene – an addition homopolymerPolystyrene – an addition homopolymer

polystyrene sheets polystyrene rods

Cups, plates and containers made from styrofoam.

© 2003 John Wiley and Sons Publishers

Polystyrene FoamPolystyrene FoamIf you introduce gas during the polymerization

process you can turn the brittle plastic into lightweight styrofoam

© 2003 John Wiley and Sons Publishers

PVC – a highly versatile homopolymerPVC – a highly versatile homopolymer

A broken car window made of safety glass containing a PVC film

© 2003 John Wiley and Sons Publishers

Polyurethane – another highly versatile homopolymerPolyurethane – another highly versatile homopolymer

Polyurethane is an incredibly resilient, flexible, and durable manufactured material that can take the place of paint, cotton, rubber, metal, and wood in thousands of applications across all fields.

Polyurethane might be hard, like fiberglass, squishy like upholstery foam, protective like varnish, bouncy like rubber wheels, or sticky like glue.

Latex paints are based on Latex paints are based on water soluble polymerswater soluble polymers

Changing the properties of Changing the properties of plasticsplastics

PlasticizersPlasticizers – makes polymers more flexible

PigmentsPigments – add colors to polymers

Fillers Fillers – change the bulk properties of plastics (increased strength)

StabilizersStabilizers – improve polymer properties (antioxidants, UV stabilizers, heat

stabilizers)

Plastics – problems with Plastics – problems with disposaldisposal

Unlike many natural materials, synthetic polymers are not biodegradable

Polymers are also resistant to breakdown by water and sunlight

Most polymers cannot be incinerated because they produce toxic gases when burned

So how do we dispose of So how do we dispose of plastics ?plastics ?

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Plastic waste in household trashPlastic waste in household trash

http://www.youtube.com/watch?v=pQEG2oLLCwk

Plastics – disposal Plastics – disposal solutionssolutions

Short term solution – recycling

Long term solution – modifying plastics to make them degradable

Incorporate a biodegradable polymer, such as starch or cellulose

Introduce chemical activators to make polymers susceptible to sunlight and moisture

Biodegradable PlasticsBiodegradable Plastics

• plastics that will naturally decompose

• made from corn-derived sugar polymers

• production is expected to reach 50 billion pounds within 5 years

• this would be a 10% market share

• The heaviest hitter in the beverage industry is taking a swing at biobased materials. Coca-Cola has now introduced bottles for its Dasani-brand water with up to 30% biobased content.

• Beverage bottles are typically created from polyethylene terephthalate (PET), made, in turn, by reacting ethylene glycol and terephthalic acid. The ethylene glycol in the new Dasani bottles will be derived from sugar and molasses, rather than its usual origin in petroleum and natural gas.

• Coca-Cola's goal is to introduce bottles made with materials that are 100% recyclable and renewable.

Biobased Plastic BottlesBiobased Plastic Bottles

Alex Tullo, Chemical & Engineering News

Closed loop recycling works best

Waste DisposalWaste Disposal

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The problem with plastic recycling is that The problem with plastic recycling is that there are many different types of plasticsthere are many different types of plastics

How can the consumer sort this out?How can the consumer sort this out?

Identification codes for plastic recyclingIdentification codes for plastic recycling

Recycling plasticsRecycling plastics

Even though we are recycling more plastic than ever in the U.S.,

we are recycling less plastic by percentage

(1 in 5 plastic soda bottles in 2008 vs. 1 in 3 in 1995)

http://www.youtube.com/watch?v=K3u5MtZ6O3U

Paper or plastic ?Paper or plastic ?

Weight and volume of 1000 bags

What are the issues that need to be considered:

• energy required to produce

• capacity and costs to reuse or recycle

• hazards to the environment

• disposal options (incineration, landfills)paper generates less toxic gases when incineratedpaper degrades in landfills more rapidly than plastic

however paper takes more space in landfills http://www.youtube.com/watch?v=vhmg6l_WNSE

Composition of municipal solid wasteComposition of municipal solid waste

100 billion pounds of plastic is produced in the U.S. each year and much of this ends up in landfills

Plastic waste is still only a small part of the disposal problem, but its use and volume is growing

Polymers and Plastics, Polymers and Plastics, reviewreview

• plastics have an amazing diversity of properties and wide ranging uses

• polymers can be formed by either addition or condensation of monomers

• natural polymers include cellulose and rubber

• six of the over 60,000 synthetic polymers provide most of the plastic products in use today

Polymers and PlasticsPolymers and Plastics

• the properties of polymers depends on the types of monomers and how they are linked together

• additives can further alter and extend the properties of plastics

• many approaches are being examined to solve the problems with plastics disposal

• source reduction and reuse are the preferred methods of decreasing plastic waste