The World of Polymers and Plastics What are plastics made from? Why are plastics important? What happens to recycled plastics and polymers? And the most important question of all - paper or plastic?

What do you think of when you hear the word “plastic”? Rayon Nylon Lycra polyurethane Teflon Styrofoam Saran

Plastics are found everywhere 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 use http://www.youtube.com/watch?v=FJAHuhFptFo http://www.freesciencenews.org/FreeTeacherVideos/

Polymers have been with us since the beginning of time 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.

Plastics are Polymers What is a polymer? 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.

All plastics are polymers formed from chains of smaller molecules

Polymers can be formed from the same type of monomer or from a combination of monomers A representation of a monomer A representation of a polymer made of one type of monomer A representation of a polymer made of two different types of monomers

Polymers can be classified based on the structures of their monomers Homopolymers consist of chains in which every monomer is identical Copolymers (or heteropolymers) are composed of chains with two or more different types of monomers

Polymers can also be classified based on the type of reaction that is used to create them Polymers are called addition polymers when each monomer is added sequentially to the growing chain without any losses Condensation polymers are formed when each monomer combines with the loss of a small molecule (such as water)

Addition polymerization is the process of linking © 2003 John Wiley and Sons Publishers Addition polymerization is the process of linking small molecules together to form chains ethylene polyethylene

Cellulose is a natural condensation polymer © 2003 John Wiley and Sons Publishers Cellulose 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 polymers Three of the six most common polymers are:

The other three of the “Big Six” are: What makes one polymer different from another?

The properties of plastics depend on their molecular structures Plastics have a wide range of properties The properties of plastics depend on their molecular structures 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.

Polymer Properties Thermoplastics – polymers that soften when heated but become firm when cooled (examples: water bottles, compact discs) Thermosetting plastics – soft enough to be molded but become firm when heated (examples: plastic pipes, car parts) Elastomers – polymers that stretch easily but return to their original shape (example: rubber)

© 2003 John Wiley and Sons Publishers Rubber is a natural elastomer Rubber forms by addition polymerization of isoprene

© 2003 John Wiley and Sons Publishers Another synthetic elastomer is also used because of its resistance to heat and solvents This is an addition homopolymer called neoprene

© 2003 John Wiley and Sons Publishers The elastomers neoprene and styrene-butadiene rubber make up the bulk of auto and truck tires

Some applications of different types of plastics

Some Uses for Phenolic Resins

© 2003 John Wiley and Sons Publishers Nylon is another synthetic condensation copolymer It consists of alternative monomers of diaminohexane and adipic acid

© 2003 John Wiley and Sons Publishers The formation of a strand of nylon 6,6 as two chemicals, dissolved in solvents that do not mix, react with each other. Nylon is formed as the two monomers, dissolved in solvents that do not mix, react with each other.

Uses for Nylon Nylon refers to a whole class of polyamides most familiar as the fiber used in stockings and carpets, but much of it also goes to making engineering polymers. In 2008, these polymers made up about 44%, or about 4.5 billion lb, of global nylon demand. used in applications that get a lot of wear and tear, such as power-tool housings, door handles, brackets, and structural components found under car hoods or in baby carriages. The basic advantage of nylon is that it combines classic thermoplastic properties—low weight and high capability of integrating different functions into one component—with its specific material properties, namely high thermal and chemical stability. This enables nylon to substitute for many metal or other material applications in terms of weight, cost, and performance.

Stretching or “necking” a plastic bag Why does the plastic stay distorted after it is pulled? Because the molecular structure is changed ! Pulling on a piece of PE The molecular rearrangement that occurs as PE is stretched

Branching alters the physical properties of PE linear PE branched PE Low density PE (LDPE) soft, stretchy, not very strong High density PE (HDPE) greater rigidity and strength

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

Disorganized polymeric strands of low-density polyethylene. © 2003 John Wiley and Sons Publishers Disorganized polymeric strands of low-density polyethylene.

© 2003 John Wiley and Sons Publishers Polymeric strands of high-density polyethylene with regions of crystallinity.

Different properties dictate different uses

© 2003 John Wiley and Sons Publishers PET – 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 Food storage bags made of poly(ethylene terephthalate) PET.

© 2003 John Wiley and Sons Publishers Polystyrene – an addition homopolymer polystyrene sheets polystyrene rods

Cups, plates and containers made from styrofoam. © 2003 John Wiley and Sons Publishers Polystyrene Foam If you introduce gas during the polymerization process you can turn the brittle plastic into lightweight styrofoam Cups, plates and containers made from styrofoam.

© 2003 John Wiley and Sons Publishers PVC – a highly versatile homopolymer

A broken car window made of safety glass containing a PVC film © 2003 John Wiley and Sons Publishers A broken car window made of safety glass. A sheet of polyvinylacetate sandwiched between two sheets of glass prevents the broken glass from disintegrating into flying slivers. A broken car window made of safety glass containing a PVC film

Polyurethane – 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 water soluble polymers

Changing the properties of plastics Plasticizers – makes polymers more flexible Pigments – add colors to polymers Fillers – change the bulk properties of plastics (increased strength) Stabilizers – improve polymer properties (antioxidants, UV stabilizers, heat stabilizers)

Plastics – problems with disposal 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 plastics ?

Plastic waste in household trash © 2003 John Wiley and Sons Publishers Plastic waste in household trash http://www.youtube.com/watch?v=pQEG2oLLCwk

Plastics – disposal solutions 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 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

Biobased Plastic Bottles 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. Alex Tullo, Chemical & Engineering News

Waste Disposal Closed loop recycling works best

© 2003 John Wiley and Sons Publishers The problem with plastic recycling is that there are many different types of plastics How can the consumer sort this out?

Identification codes for plastic recycling

Recycling plastics http://www.youtube.com/watch?v=K3u5MtZ6O3U 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 ? 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 incinerated paper degrades in landfills more rapidly than plastic however paper takes more space in landfills http://www.youtube.com/watch?v=vhmg6l_WNSE Weight and volume of 1000 bags

Composition 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, review 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 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