This slide set was used to create the MaterialsConcepts YouTube Video "Muddiest Points: Polymers I - Introduction". Here is the link to that video: https://www.youtube.com/watch?v=D0I7ukw18FE To study the vocab used in this video, visit this site: http://quizlet.com/21161469/61-polymers-ia-concepts-terms-flash-cards/ This work was supported by NSF Grants #0836041 and #1226325

1. Muddiest Points
Muddiest Points:
• “I don’t get the difference between a monomer, a
mer, and a polymer?”
• “How do I calculate degree of polymerization?”
• “How does degree of polymerization affect polymer
properties?”
• “I don’t get polymer microstructures and how they
affect properties?”
• “I don’t get the different techniques for processing
polymers.”
Polymers I: Introduction to Polymers

2. What is a Polymer?
Poly mer
Many Units
repeat
unit
repeat
unit
repeat
unit
What is a Polymer?
Definition:
PE Milk Container PVC Pipe PP Rope

3. •C-C rotations along the chain give the polymer
molecule a loosely-coiled, string-like shape
Polymer Chain Geometry
Carbon
Hydrogen

4. What are Important Polymer Concepts & Terminology?Monomers, Mers, Polymers, and Degree of Polymerization
Degree of Polymerization:
Concept and Definition
• Monomer - small, unreacted single molecule for
polymer.
Ethylene Monomer:
• Mer – single repeat unit of a polymer
Polyethylene Mer:
2 C-C chain bonds / mer
• Polymer – entire polymer chain
Polyethylene Molecule:
n mers / chain molecule
n = degree of polymerization (DP) = n mers / chain molecule
n= DP =
n = DP =
• n is typically 100  10,000 but may go higher than 100,000
number of mer units
polymer molecule
molecular weight of polymer molecule
molecular weight of mer
Hydrogen
Carbon
Ethylene Monomers

5. Candle
(Paraffin)
Container
(HDPE)
n (DP) 10 10,000
MW Chain
(g/mol)
(28 g/mol )(10) =
280 g/mol
(28 g/mol)(10000) =
280,000 g/mol
Tm (°C)
MW of Molecule = n * MW Mer
2.Why does the Tm increase with
more C atoms in chain?
1. What are the similarities and
differences of candles and
plastic milk containers?
How Degree of Polymerization Affects Properties: Melting Point
n= Degree of Polymerization (DP) Molecular Weight= MW
Temperature(°C)
Number of carbons= 2n = 2* DP

6. What are the Four Different Types of
Polymer Structure and Morphology?
• Polymer – a long chain molecule of 1-D covalently bonded repeat
units or a network of 3-D covalently bonded repeat units
• Length of molecule varies from 1,000s to 100,000s of atoms long.
• Four main classes of polymer solids we will consider are:
–Thermoplastic AMORPHOUS polymers are 1-D covalently-bonded chains.
They are randomly-oriented and form a glassy solid. When heated, they melt;
when cooled, they solidify; and they can be remelted (melt recyclable).
- Thermoplastic SEMICRYSTALLINE polymers also have 1-D covalently-bonded
chains. They form layers of thin, chain-folded crystalline lamellae separated
by amorphous regions and are connected with tie molecules. When
heated, they melt. When cooled, they solidify and can be remelted (melt
recyclable).
– Heat Set ELASTOMERS are 3-D LIGHTLY to MODERATELY crosslinked
networks of long chain molecules that are covalently crosslinked during a
curing chemical reaction. After the cure, the 3-D network maintains its
structural integrity when heated (not melt recyclable).
–Heat Set THERMOSETS are 3-D HIGHLY crosslinked networks of covalently-
bonded molecules. The thermoset reaction forms a rigid amorphous solid
with very good thermal resistance (not melt recyclable).
PS Glass
PE Trash Bag
Rubber Shoe Sole
Bakelite Billiard Balls

7. How can Polymers be Classified?

8. What is the Effect of Structure & Morphology on Mechanical Properties?
Polymer
E
(MPa)
TS
(MPa)
%EL
Natural
Rubber
2.5 20
600-
1000%
HDPE 830 28
300-
600%
Polystyrene 3100 40
1.2-
2.5%
Bakelite 6900 55 0.1%
A
B
C
PS Glass PE Trash Bag
Rubber Shoe Sole
D
Bakelite Billiard Balls

9. Morphology and Thermal & Mechanical Properties
Lightly X-linked
Elastomer
Heavily X-linked
Thermoset
Semicrystalline
Polymer
Amorphous
Polymer
Thermoplastic Polymers Heat Set Polymers
Tg = 100C
T25 < Tg
Glassy
Tg = -103C
Tg < T25
Elastic
Tg = -90C; Tm = 130C
Tg < T25 < Tm
Flexible
Tg = 163C
T25 < Tg
Rigid
Tg = Glass Transition Temperature, below which a polymer is rigid and brittle
PS Glass PE Trash Bag Rubber Shoe Sole Bakelite Billiard Balls

10. 1010
What is the Effect of Structure on Processing of Plastics?
• Thermoplastics – Amorphous & Semicrystalline
• Processing can be continuous – only cooling required
• Heat to melt, shape & cool below Tg or Tm
• Can be reversibly melted and solidfied, i.e. recyclable
• Ex: PE, PP, PS.
• Heat Sets – Thermosets and Elastomers
– Processing not continuous – one part at a time
– Heating & crosslink reaction require time in fixed shape mold
– Permanent 3-D crosslinked network – not recyclable
– Shape is permanent – does not change with heat; will only degrade
– Elastomer + crosslink agent (S, O) mixed, shaped, reacted
– Ex. polybutadiene, polyisoprene
– Thermoset prepolymer pressed into a shape & reacted
– Ex: Bakelite, urethane, epoxy
For additional information on polymer processing terminology go to:
GOOGLE “matsciasu” and get Quizlet.com vocabulary e-flash cards for 6.2 Polymers II – Processing
PS Glass
PE Trash Bag
Rubber Shoe Sole
Bakelite Billiard Balls

11. Processing for Thermoplastic and Crosslinked Polymers
PS Glass PE Trash Bag
Rubber
Shoe Sole
Bakelite Billiard
Balls
Thermoplastic
Amorphous
Thermoplastic
Semicrystalline
Heat Set
Elastomers
Heat Set
Thermosets
Processing:
Film Blowing
Processing:
Injection Molding
Processing:
Transfer Molding
Processing:
Compression Molding

12. Effect of Molecular Weight and Bonding on Properties
Metals Ceramics Polymers
0.2
8
0.6
1
Wood( gr
AFRE( fib
CFRE*
GFRE*
Glass fibers
Carbon fiber
Aramid fiber
Epoxy only
0.4
0.8
2
4
6
10
20
40
60
80
100
200
600
800
1000
1200
400
CFRE( fib
GFRE( fib
GFRE(|| fib
AFRE(|| fib
CFRE(|| fib
Why is elastic modulus of polymers two orders
of magnitude less than metals or ceramics?
How do Polymer Properties Compare to Metals and Ceramics?
Property Polymer Metal Ceramic
E (GPa) 0.2-4 40-400 10-1200
Tensile Strength
(Mpa)
26-60
(Fibers~700)
200-3400 70-140
Ductility
(% elongation)
2-500 1-8 1<
Tm (°C) 100-250 200-2800 500-4000
Coefficient of
Thermal
Expansion
(m/m-K)
15 x10-6 -
100 x10-6
5x10-6 -
12x10-6
1x10-6 -
5x10-6
E(GPa)

13. Wrap-Up
• “What is a polymer?”
• “I don’t get the difference between a mer and a
monomer.”
• “How do I calculate degree of polymerization?”
• “How does degree of polymerization affect polymer
properties?”
• “I don’t get polymer microstructures and how they
affect properties.”
• “I don’t get the different techniques for processing
polymers.”
Polymers I: Introduction to Polymers