Polymers are large molecules composed of repeating structural units called monomers. The most common polymers are polyethylene, polypropylene, polystyrene, and polyvinyl chloride. Polymers can be classified as natural or synthetic, and as thermoplastics, thermosets, or elastomers depending on their molecular structure and response to heat. Common applications of polymers include plastic bags, clothing, containers, pipes, and electrical insulation.

1. A brief introduction
to polymers
July 24, 2014

2. What is a polymer
• A polymer is large [big] molecule made
up of repeating units of a smaller
molecules called as Monomers.
• Polymer : derived from Greek [ ‘poly’
means many and “meros” means parts.
• Examples : Polyethylene [PE], Polystyrene [PS]

3. Carbon Chains are the Backbone
of Polymers
• Carbon has four valence electrons and
will make four bonds.
• Carbon can bond with itself and form
long chains
• Other elements used in polymers
– Hydrogen
– Oxygen
– Nitrogen
– Chlorine
– Fluorine
– Silicon

4. The word, polymer, implies that polymers are constructed
from pieces (monomers) that can be easily connected into
long chains (polymer). When you look at the above shapes,
your mind should see that they could easily fit together.

5. Suppose our repeat unit is an “X.” Then, a linear
polymer based on “X” would look like the
following:
… --X--X--X--X--X--X--X--X--X--X--X--X--…
where each “X” represents a “mer.”

6. • Naturally occurring polymers have been used
for thousands of years
– wood, rubber, cotton, wool, leather, silk,.. Etc
• Artificial polymers are, indeed, relatively
recent and mostly date from after WW-II
– in many cases, the artificial material is
both better and cheaper than the natural
alternative

7. Crude oil is a mixture of assorted
polymers that can be separated by
fractional distillation

9. Properties of Polymers
• vs other materials
– Lower density
– Lower mp
– High molecular weight
– Opaque to transparent
– Rigid to flexible
– Bouncy? Inelastic?
– Absorb water? Repel
water?
• ADVANTAGES
– Color range
– Insulator
– Light weight
– Corrosion resistant
– Easy to process
• DISADVANTAGES
– Difficult to repair
– Odors??
– Unstable at high temps
– Can be costly
– Subject to deterioration by
solvents
– Can be toxic

10. Polymer Powders
Samples
• Water lock
– hydrophilic (having affinity for water)
– absorbs 800x its mass in distilled water.
– add Salt

11. • Water molecules
are attracted to
the negative
charges by
hydrogen bonding.
• Recall this is the
attraction
between H and O
due to polar
bonds
ABOUT SODIUM POLYACRYLATE

12. Polymer Powders
Samples
• Instant Snow
– A cross linked hydrophilic powder

13. Polyacrylate, But Different
• Instant Snow is the same
material, but the structure
is different so the water
molecules become
absorbed inside the
polyacrylate so it expands
and feels dry
• Grow beasts and shapes
are similar in that they
absorb water and expand

14. Polymer Powders
Samples
• HDPE powder
– hydrophobic (afraid of water)

15. Polymer Powders
Samples
• Water Gel Crystals and Spheres
– hydrophilic with semi-permeable cover
– ghost crystals
– index of refraction
• Grow beasts

16. Polymer Powders
• Water lock
– Hydrophilic
• Instant Snow
– Hydroscopic crosslink
• HDPE Powder
– Hydrophobic
• Gel Crystals
– Hydroscopic with semi-permeable cover

17. distilled water tap water
0.45% salt
water
0.9% salt
water
no water

18. Ways to Classify Polymers
• Natural vs. Synthetic
• How They Join (Type of Polymerization)
– Addition
– Condensation
• How They Respond to Heat
– Thermoplastics
– Thermosets

19. Natural and Synthetic Polymers
Natural Synthetic (man-made)
• Skin ▪ Plastic bags
• Cotton ▪ Polyester fiber
• Starch ▪ Glue
• Latex (natural rubber) ▪ synthetic Rubber
• Silk ▪ Polyurethane Foams
• Vitamin C ▪ Vitamin C
• Cellulose ▪ Polyethylene
NOTE: Our resource for the raw materials to
make synthetic polymers is oil (petroleum).

20. Polymers
Natural vs Synthetic
• Natural
– Rubber (latex)
– Cotton
– Wool
• Synthetic
– Plastics
– All around us
• Clothes, containers, packaging, etc…

21. Industrially Important Polymers
Polyethylene (PE)
POLYMER MER APPLICATIONS
Polypropylene (PP)
electrical wire insulation,
flexible tubing, squeeze
bottles
carpet fibers, ropes, pipes
liquid containers (cups,
buckets, tanks)

22. Industrially Important Polymers
Polystyrene (PS)
POLYMER MER APPLICATIONS
Polyvinyl Chloride
(PVC)
packaging foams, egg cartons,
lighting panels, electrical
appliance components
bottles, hoses, pipes, valves,
electrical wire insulation,
toys, raincoats

25. Polyethylene
LDPE (sandwich wrap)
• Low density polyethylene (trees with branches)
HDPE (milk jug)
• High density polyethylene (trees without branches)

27. Polymer Structures
• Linear Polymers
• Branched Polymers
• Cross-Linked Polymers
• Networked Polymers

28. Various Polymer Structures

29. Linear Structure
• Molecules are free to move. Slide back
& forth against each other easily, so
they are thermoplastic: can be
reshaped or reformed with heat.

30. Branched Structure
• Side chains prevent easy movement.
More heat required to soften, but still
mostly thermoplastic.
Side chain

31. Cross-linked Structure
• Adjacent molecules have formed bonds, so
individual molecules can’t slide past each
other. They retain their shape when heated,
so are thermoset: cannot be reformed with
heat (not recyclable).

32. Holding chains together
• covalent bonds – stronger – ex. rubber
• intermolecular forces – weaker – ex.
slime
• entanglement – ex. HDPE –
– (analogy: 50 pieces of yarn – each 6 feet
long – jumble and wad them up – throw them
down in a pile on the ground – try to pull out
one piece – what happens???)

33. Polymer Networks Include amorphous and
crystalline regions:

35. Classifying Polymers: Response to Heat
• Thermoplastic
–Reforms/reshapes with heat
–All recyclables
–Milk jug
• Thermoset
–Sets with chemical reaction
• Elastomer
–Is elastic

36. Polymers
• Timeline of Plastics
• 1868 Cellulose Nitrate
• 1900 Viscose Rayon
• 1909 Phenol-Formaldehyde
• 1927 Cellulose Acetate
• 1933 Polyethylene
• 1936 Acrylic or Polymethyl Methacrylate
• 1938 Polystyrene
• 1939 Nylon
• 1941 Polyethylene Terephthalate
• 1942 Low Density Polyethylene
• 1942 Unsaturated Polyester
• 1957 Polypropylene
• 1964 Polyimide
• 1970 Thermoplastic Polyester
• 1978 Linear Low Density Polyethylene
• 1985 Liquid Crystal Polymers