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