chapter 8-- Polymers

Review Notes

prepared Dec 1, 2001

Some obvious questions:

Posed here as fill in the blank or short answer questions.

• what is a polymer?
• another name for a polymer is a _______-molecule
  • Polymers or macromolecules are very large (long) molecules
  • Size often means a carbon chain that is thousands to 10⁵ atoms long.
  • There are generally made by joining many small molecules, known as monomers
• what is meant by the term "plastic" (two different meanings)
  • Plastic really means easily distorted or moldable (like modeling clay.)
  • Since most synthetic polymers have this property to some extent, they tended to be labeled as plastics.
  • Today the term "plastic" is often used to mean "synthetic polymer"
• what are the two main styles of polymers
  • We divide polymers into thermoplastic and thermosetting
  • thermoplastic materials become plastic (soften, deform, can be shaped) when heated
  • thermosetting materials do not soften and can not be reshaped after creation
  • there are few thermosetting plastics in wide use (none of the top six, for example)
  • manufacturing products is much easier and faster if heating permits shaping the desired object, cooling makes it hold its shape
• name two naturally occurring polymers
  • polymers have been around for millions of years before we knew how to make them (or even knew what the term meant.)
  • proteins are one major category
    • this includes fibers like wool, silk, spider webs
    • this also include the structural parts of muscle tissue-- widely distributed
  • cellulose is another major form of natural polymer
    • cotton fiber, the fibers in wood and what ends up as paper
    • wood pulp is treated to remove a binding protein called lignin to free the cellulose
• name two man made modifications of natural polymers
  • nitrocellulose (treating cellulose with nitric acid)
    • becomes useful (moldable material) when mixed with camphor-- called celluloid
    • used for synthetic ivory, movie film, varnishes
  • rayon
    • chemical treatment dissolves cellulose
    • the solution is squirted through tiny nozzles
    • the solid cellulose reforms
    • now a very fine, very long fiber (rayon)
• what's the oldest synthetic polymer
  • Bakelite
    • made from formaldehyde and phenol
    • a thermosetting plastic
    • hard, heat resistant, good electrical insulator
    • made about 1907
• how does the production volume of metal compare to the production of plastics?
• on a volume basis the US produces more plastic than metals
• this is a little biased-- the balance tips towards metals if you go by weight
• there's also much more metal recycling
• but, that's still a lot of plastic and plastic has replaced metals in many applications
• polymers are formed by two basic types of reaction: name them; briefly describe the reactions
  • addition reactions-- typically two carbon chains with a double bond link up using the electron pair from the second bond of the double blond.
  • condensation reaction-- joins two different groups on adjacent molecules, and also produces (frees) a small molecule such as water.
• name several of the six most widely used polymers
  • (see text, figure for this one)
• what's the name for the basic unit in a polymer? ______________
  • monomer (logically question goes earlier and is usually needed to answer "what is a polymer?")
• which plastic is most likely to end up in beverage bottles?
• most foam products (like foam coffee cups) are made from _______________
  • pop bottles are PETE ; foams are polystyrene
• what steps are required to recycle / reuse a polymer
  • collection of the used material
  • washing
  • chipping
  • separating from other plastics (earlier or now by density and flotation)
  • thermoplastics can be used directly
    • sometime material is returned and chemically reprocessed
    • to be honest, incineration and use for heat or electricity is probably a reasonable form of recycling or at least reuse
• polyethylene is manufactured from _______ through the use of a _________.
  • a catalyst is used to convert ethylene into polyethylene
  • what technique changes polyethylene from a low density soft plastic to a denser, more rigid material? (a molecular answer)
    • cross linking
• How many bonds does a carbon atom normally have?
• How many bonds does a hydrogen atom normally have?
• C forms four bonds, H forms 1 bond (oxygen forms 2, Nitrogen 3)
• what is the common structural feature of alcohol molecules
  • -O-H connected to the carbon chain
• as ester is formed by the reaction of a _____ and a __________
• an amide is formed by the reaction of a ______ and a _________
  • esters form from alcohol and carboxylic acid
  • amides form between an amine and a carboxylic acid
  • (you should certainly be able to recognize and label these functional groups)
• an example of a polyester is _____
  • nylon is characterized as a poly- _______
  • proteins are ___ synthetic products or ___ natural products? (select one)
  • a protein is made from small molecules called ____________
  • a protein is an example of a poly- _________
  • rayon is an example of _________________
  • PETE is the only common polyester in the big six
  • nylon (like protein) is a polyamide
  • proteins form from amino acids (molecule with both amine and carboxylic acid group)
  • rayon (see above) is a form of cellulose
• why is manufacturing waste (plastic) easier to recycle than post consumer waste?
  • little collection is required-- it's all found at the manufacturing site
  • the people collecting it know exactly what it is-- no sorting
  • the history is known -- no questions about what has been in contact
  • generally, never used-- no need to clean or even remove labels
• most commercial plastics are made from ____________.
  • petroleum
• would a switch from plastic bags and plastic foam coffee cups to paper products be environmentally desirable? List several pro- and con- in the arguments.
• what are some desirable properties of a commercial polymer?
  • these are long answers and check the book
  • it's not clean paper is environmentally more friendly or less demanding of oil
  • properties include strength, light weight, transparent, impact resistance, impermeable to gas, cheap-- and especially, relatively low cost ways to fabricate objects
• Paints and varnishes involve polymerization (traditional oil based materials)
  • is that the same as paint drying?
  • what is typically the "trigger" for polymerization of a paint?
    • these have oils with double bonds
    • polymerize on exposure to oxygen
    • paint dries when solvent evaporates
    • polymerization (getting tough) takes up to a few days
• Most plastics are manufactured from petroleum. How does the amount of plastic compare with more conventional uses of oil for combustion/energy and for lubrication. (Figure 9.15)
  • the figure shows that fuels and lubrication uses are much larger
• Discuss biodegradation and polymers.
  • see text, but basically polymers just don't naturally degrade once discarded.
  • it may be desirable to modify plastics to encourage destruction of a plastic after a period of a few months or years.
  • obviously not a great idea for plastic decks, boats, car bodies-- but maybe for plastic bags. Pop bottles and ketchup containers better not decompose for a year or two or the shelves of my pantry will be a mess.

3, 10, 15, 17, 21, 22, 25,