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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
© 2003 John Wiley and Sons Publishers
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.
© 2003 John Wiley and Sons Publishers
Polymeric strands of high-density polyethylene with regions of crystallinity.
© 2003 John Wiley and Sons Publishers
Different properties dictate different usesDifferent properties dictate different uses
© 2003 John Wiley and Sons Publishers
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 ?
© 2003 John Wiley and Sons Publishers
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
© 2003 John Wiley and Sons Publishers
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