1. POLYMERS “Plastics”

2. D14, D15, D17
D14 - Describe combustion reactions of hydrocarbons and their resulting by- products.
D15 - Explain the general formation and structure of carbon-based polymers, including synthetic polymers, such as polyethylene, and biopolymers, such as carbohydrate.
D17 - Explain how the chemical structure of polymers affects their physical properties.

3. What is a Polymer?
Any of numerous natural and synthetic compounds consisting of up to millions of repeated linked simple Carbon based molecule called monomers.

4. Polymerization Monomers are simple carbon molecules
Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain.

5. Natural Polymers (Biopolymers)
Examples:
Cellulose
Shellac
Amber
Proteins
Nucleic Acids
Hair and Fur

6. Synthetic Polymers Nylon Neoprene PVC Polystyrene Silicone
Examples:
Nylon
Neoprene
PVC
Polystyrene
Silicone
Silly Putty ®
Plastics

7. Some Common Polymers Name(s) Formula Monomer Properties Uses
Polyethylene low density (LDPE)
–(CH2-CH2)n–
ethylene CH2=CH2
soft, waxy solid
film wrap, plastic bags
Polyethylene high density (HDPE)
rigid, translucent solid
electrical insulation bottles, toys
Polypropylene (PP) different grades
–[CH2-CH(CH3)]n–
propylene CH2=CHCH3
atactic: soft, elastic solid isotactic: hard, strong solid
similar to LDPE carpet, upholstery
Poly(vinyl chloride) (PVC)
–(CH2-CHCl)n–
vinyl chloride CH2=CHCl
strong rigid solid
pipes, siding, flooring
Poly(vinylidene chloride) (Saran A)
–(CH2-CCl2)n–
vinylidene chloride CH2=CCl2
dense, high-melting solid
seat covers, films
Polystyrene (PS)
–[CH2-CH(C6H5)]n–
styrene CH2=CHC6H5
hard, rigid, clear solid soluble in organic solvents
toys, cabinets packaging (foamed)
Polyacrylonitrile (PAN, Orlon, Acrilan)
–(CH2-CHCN)n–
acrylonitrile CH2=CHCN
high-melting solid soluble in organic solvents
rugs, blankets clothing
Polytetrafluoroethylene (PTFE, Teflon)
–(CF2-CF2)n–
tetrafluoroethylene CF2=CF2
resistant, smooth solid
non-stick surfaces electrical insulation
Poly(methyl methacrylate) (PMMA, Lucite, Plexiglas)
–[CH2-C(CH3)CO2CH3]n–
methyl methacrylate CH2=C(CH3)CO2CH3
hard, transparent solid
lighting covers, signs skylights
Poly(vinyl acetate) (PVAc)
–(CH2-CHOCOCH3)n–
vinyl acetate CH2=CHOCOCH3
soft, sticky solid
latex paints, adhesives
cis-Polyisoprene natural rubber
–[CH2-CH=C(CH3)-CH2]n–
isoprene CH2=CH-C(CH3)=CH2
requires vulcanization for practical use
Polychloroprene (cis + trans) (Neoprene)
–[CH2-CH=CCl-CH2]n–
chloroprene CH2=CH-CCl=CH2
tough, rubbery solid
synthetic rubber oil resistant

8. Resin Identification Code
Symbol Abbreviation Polymer Type PET or PETE Polyethylene Terephthalate HDPE High Density Polyethylene PVC Polyvinyl Chloride or Vinyl LDPE Low Density Polyethylene PP Polypropylene PS Polystyrene Other Polymers or blends of polymers that do not fall into the other 6 classifications.

9. Properties of Polymers (6)
Polymers can be very resistant to chemicals that can break down other materials.
Polymers can be both thermal and electrical insulators.
Generally, polymers are very light in weight with significant degrees of strength.

10. Properties of Polymers cont.
Polymers are materials with a seemingly limitless range of characteristics and colors.
Polymers are usually made of petroleum, but not always. 
Polymers can be used to make items that cannot be made from other materials.

11. Inter-chain bonding (cross-links)
The three factors that influence the degree of stiffness of a plastic are:
Chain length
Chain branching
Inter-chain bonding (cross-links)
As a rule, mechanical properties such as ductility, tensile strength, and hardness rise and eventually level off with increasing chain length.
The importance of the first two factors is nicely illustrated by the differences between HDPE and LDPE.

12. HDPE vs LDPE
High Density Polyethylene (HDPE) is composed of very long unbranched hydrocarbon chains.
These materials, while being relatively strong and stiff, retain a degree of flexibility.
Low Density Polyethylene (LDPE) is composed of smaller and more highly branched chains.
This material is therefore softer, weaker, less dense and more easily deformed than HDPE.

13. Linear vs. Branched

14. There are two Plastic Types
Thermoplastic Polymers
Thermoset Polymers

15. Thermoplastic Polymers
A Thermoplastic is a polymer in which the molecules are held together by weak forces.
These soften when exposed to heat and return to its original condition when cooled back down to room temperature.
When a thermoplastic is softened by heat, it can then be shaped by extrusion, molding, or pressing.
Examples include milk jugs and carbonated soft drink bottles.

16. Thermoset Polymers
A Thermoset is a polymer that solidifies or “sets” irreversibly when heated or cured. A thermoset polymer can’t be softened once “set”. Thermosets are durable and strong They are used extensively in automobiles and construction including applications such as adhesives, inks, and coatings. The most common thermoset is a rubber tire

17. Recycling Thermoplastics vs. Thermosets
Thermoplastic: these are polymers that can be repeatedly softened or melted by heating
These can be recycled by heating and reforming.
Thermoset: cross-linked polymers that do NOT soften when heated because strands are not free to move.
More cross-links = greater strength
These are not easy to recycle and can only be cut or chopped into smaller pieces

18. Thermoset: Vulcanized Rubber used to make strong tires

19. Thermoplastics Remember the analogy to a plate of cooked spaghetti

20. Thermosets:

21. What happens when we are done using a polymer product??

22. Durables vs. Non-Durables
Products with a useful life of three years or more are referred to as durables.
They include appliances, furniture, consumer electronics, automobiles, and building and construction materials.
Products with a useful life of less than three years are generally referred to as non-durables.
Common applications include packaging, trash bags, cups, eating utensils, sporting and recreational equipment, toys, medical devices and disposable diapers.

23. What do we do with Polymers when they are no longer useful
What do we do with Polymers when they are no longer useful? Three options and their consequences
Disposal in a landfill
Incineration
Recycling

24. Disposal in a landfill
ACTION: Polymers take a very long time to decompose if just buried in a landfill. CONSEQUENCE: Polymers placed in a landfill take up a lot of space and could possibly react with other materials to result in compounds that could be potentially harmful to the environment.

25. Incineration
ACTION: Incineration is the burning (combustion) of polymers.
CONSEQUENCE: Incineration produces harmful gases that are toxic to the environment.

26. Why is incineration dangerous?
The Chemical Reaction for Combustion
Hydrocarbon + O2  CO2 + H2O
The complete combustion of hydrocarbons results in two products – Carbon dioxide and water.

27. Products of Incineration
Complete combustion results in the release of CO2, which is a greenhouse gas
Incomplete combustion occurs if oxygen is in insufficient supply. This results in the release of CO (carbon monoxide) which is dangerous for organisms.

28. Recycling
ACTION: Recycling is a process during which waste materials are re-used in different ways to form new products.
CONSEQUENCE: Recycling prevents waste of potentially useful materials, and reduces the consumption of fresh raw materials.

29. Recycle - The best choice!
Mechanical Recycling
Feedstock Recycling
Source Reduction

30. Mechanical Recycling
Once collected, plastics are sorted and then chopped into flakes, washed to remove contaminants and sold to manufacturers to make new products.

31. Feedstock Recycling
This is where the plastics are chemically reacted to form new substances that are used for another purpose than producing the original material.
One way in which is this done is through Pyrolysis (heating without oxygen) . This process changes polymers such as PET or nylon into new starting materials.

32. Source Reduction Use less materials!
Redesign products and packaging that uses less polymer material.
Reduce the amount the amount of polymer products that are purchased.
Clean and Reuse the polymer products that have been purchased.

33. What is the first question you are asked at the grocery store checkout?

34. Paper or Plastic?
What is the best choice?