04/01

““The World We Create”The World We Create”NATS 101NATS 101Section 6Section 6

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How we change the materials that have changed society and beyond...

These Transformations… ?

Wood:CELLULOSE

Muscle Fuel:GLYCOGEN

Arthropod Exoskeletons:CHITIN

Plant Food:STARCH

TransformingTransformingPolymersPolymers

All made from the monomerGlucose

TranslucentFlexibleStable

OpaqueNon-Permeable

Degrade ResistantFlexible

DuctileFlexibleDegradable?

StrongDenseRigid

High Tensile StrengthElastic

All made from the monomerEthylene

TransformingTransformingPolymersPolymers

Nature inspires us, but is much too complex and subtle to mimic.

Why?Why?

400Vs.

4,000,000,000

4 Hundred Years of Chemistry

Vs. 4 Billion Years of Evolution

Scientist have had to develop methods that differ from nature.

TransformingTransformingPolymersPolymers

We start with a clear liquid polymer We combine with an additive We get a slimy goo

(yes, “goo” is a technical term)

What happened in the beaker?

TransformingTransformingPolymersPolymers

What Happened?

Polymer: Polyvinyl Alcohol (PVA)Small Section of Two Chains Shown

n

n

TransformingTransformingPolymersPolymers

Weak Crosslinks Formed

Additive: Borax (Sodium tetraborate decahydrate)

Forms bonds, linking chains

n

n

Notice the dashed lines: |||||||| These represent a weaker interaction than Covalent Bonding.

TransformingTransformingPolymersPolymers

When sulfur and heat is added to rubber, the sulfur bonds to the polymer forming covalent crosslinks...

TiresTiresTransformedTransformed

SocietySociety

When sulfur and heat is added to rubber, the sulfur bonds to the polymer forming covalent crosslinks.

How would this change the properties of the rubber?

Sulfur chain length can differ – what part of a tire should get the longer and shorter chains?

Tread? Sidewalls?

Two balls are composed of the same polymer

One is much more elastic How is this achieved? A different additive perhaps?

Now it’s your turn with the balls…

Part I: Follow the directions on your worksheet to transform a liquid polymer into an elastic ball. Add the Borax slowly to the glue and observe the changes.

Part II: Perform a bounce test by dropping your ball from the top of a meter stick and observing the height of the bounce. Report your results to your TA.

TransformingTransformingPolymersPolymers

What Happened?

Polymer: Polyvinyl Acetate (PVAc)

TransformingTransformingPolymersPolymers

Crosslinker: Borax

Plasticizers: Used to soften polymers e.g. Phthalates

Fillers: Used to strengthen a polymer e.g. Inert materials like cellulose and asbestos

Stabilizers: Used to reduce polymer degradation e.g. Antioxidants, UV absorbers

Flame Retardants: Used to reduce combustibility e.g. Halogens (Cl and F atoms)

Colorants: Used to provide color e.g. Pigments (insoluble/opaque) and Dyes (soluble/transparent)

TransformingTransformingPolymersPolymers

Linear chains:

Branched chains:

Crosslinked chains:

Copolymers:

NEWNEW:

…form when different “mers” are used to form a polymer. Can be linear, branched, etc… e.g.: Nylon

BPA (Bisphenol A) is not an additive here – it combines with carbonate monomers to form a copolymer. This adds strength and chemical stability to carbonate alone.

Water bottles were being made using copolymers of carbonate and BPA…

Next Week: Why this may be a problem...

TransformingTransformingthe the

EnvironmentEnvironment