The Structure and Properties of Polymers
Also known as
Bonding +Properties
What is a polymer?
•A long molecule made up from lots of small molecules called
monomers.
Break it down…Poly- Many
Mono- One
Meros- Part “mer”
Macro- Many
Translate this…
“I’m Hermann Staudinger. I say that rubber has a polymeric structure.”
All the same monomer•Monomers all
same type (A) •A + A + A + A • -A-A-A-A-•eg poly(ethene)
polychloroethene PVC
Different monomers•Monomers of two
different types A + B
•A + B + A + B• -A-B-A-B-•eg polyamides •polyesters
http://www.umass.edu/molvis/tutorials/dna/dnapairs.htm
So what does a synthetic polymer look like?
Addition polymerisation•Monomers contain C=C bonds•Double bond opens to (link) bond to next
monomer molecule•Chain forms when same basic unit is
repeated over and over
Copolymerisation•when more than one monomer is used.• An irregular chain structure will result eg
propene/ethene/propene/propene/ethene•Why might polymers designers want to
design a polymer in this way?
Bellringer: Acid Plant Observations!
Hwk: Finish Lab Template!Hwk: Finish Lab Template!
Make Your Own Lab•Task: Design and Conduct (if time!) a lab
that will examine “stress-strain behaviors of your “Original Recipe” polymer.
•You will have tomorrow to conduct your experiment also
•There are 3 types of “stress-strain” behaviors…
Stress-Strain Behaviors•Tensile Strength
▫Amount of pulling force placed on a material before it breaks
•Abrasion Resistance▫Toughness of material against scraping,
scuffing, or scarring•Puncture Strength
▫Ability of a material to keep moving objects from perforating a surface.
Welcome Back!•Bellringer- Acid Plant Lab Observation
(only one this week!)
•Hwk- QUIA Monday 11/28 (already up!)
Congrats to Billy on finishing 41st of 526 at the Turkey
Trot 10K!
Test Next Tuesday!
Today 11/28/11•Observations
▫Make sure you get your Recycling # Sheet!
•Thanksgiving sweep!
•Strengths/Types of Polymers
What decides the properties of a polymer?•3 Main Factors:
1.) Chain Length-Longer chain = ____________
2.) Chain Branching-More branching = ___________
3.) Interchain Bonding (CROSS LINKS!!!!)
These Factors influence…•Morphology
▫Form or structure
Crystalline and amorphous polymers• Both amorphous and
crystalline areas can be in the same polymer.
•Crystalline - regular chain structure - no bulky side groups.
•Amorphous- disordered
• More crystalline
polymer = stronger and less flexible.
Thermoplastics (~85%)
•No cross links between chains.•Weak attractive forces between chains
broken by warming. (erasers, gelatin)•Change shape - can be remoulded.•Weak forces reform in new shape
when cold.
Gelatin…no cross-linking
PVC
Polyethylene terephthalate (like in disposable water bottles)
Sodium Polyacrylate – in diapers!
Polystyrene (styrofoam)
Teflon – nonstick coating on pans…also used to make Gor-Tex
Thermosets
•Extensive cross-linking formed by covalent bonds.
•Bonds prevent chains moving relative to each other.
•Best suited to high-temperature applications – can be brittle when very cold.
Examples of thermosets:•Epoxy resins•Vulcanized rubber (car tires)• Injected molded items like milk crates.
Rubber (below is a monomer)
Examples of amorphous polymers:polyproplene
Nylon
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