ch04_polymer engineering and materialss.ppt

Polymer technology

1. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
TEM of spherulite structure in natural rubber(x30,000).
•Chain-folded lamellar crystallites(white lines) ~10nm thick extend radially.
Chapter 4-Polymer Structures

2. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
ISSUES TO ADDRESS...
What are the basic
•Classification?
•Monomers and chemical groups?
•Nomenclature?
•Polymerization methods?
•Molecular Weight and Degree of Polymerization?
•Molecular Structures?
•Crystallinity?
•Microstructural features?
Chapter 4-Polymer Structures

3. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Polymer= many mers
Adapted from Fig. 14.2, Callister 6e.
Polymer Microstructure
Polyethylene perspective of molecule
A zig-zag backbone structure with covalent bonds

4. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Covalent chainconfigurations and strength:
Direction of increasing strength
Adapted from Fig. 14.7, Callister 6e.
Polymer Microstructure
Van der Waals, H
More rigid

5. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Common Examples
-Textile fibers: polyester, nylon…
-IC packaging materials.
-Resists for photolithography/microfabrication.
-Plastic bottles (polyethylene plastics).
-Adhesives and epoxy.
-High-strength/light-weight fibers: polyamides,
polyurethanes, Kevlar…
-Biopolymers: DNA, proteins, cellulose…

6. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
•Thermoplastics: polymers that flow more easily when
squeezed, pushed, stretched, etc. by a load (usually at
elevated T).
–Can be reheated to change shape.
•Thermosets: polymers that flow and can be molded
initially but their shape becomes set upon curing.
–Reheating will result in irreversible change or decomposition.
•Other ways to classify polymers.
–By chemical functionality (e.g. polyacrylates, polyamides,
polyethers, polyeurethanes…).
–Vinyl vs. non-vinyl polymers.
–By polymerization methods (radical, anionic, cationic…).
–Etc…
Common Classification

7. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Common Chemical Functional Groups
Saturated hydrocarbons
(loose H to add atoms)CC
H
H H
H
Ethylene
(ethene)CC
H
H C
H
H
H
H
Propylene
(propene)
=
1-butene
2-butene
trans cis
Acetylene
(ethyne)CCH H
Unsaturated hydrocarbons
(double and triple bonds)

8. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Alcohols Methyl alcohols
Ethers Dimethyl Ether
Acids
Acetic acid
Aldehydes
Formaldehyde
Aromatic
hydrocarbons
Phenol
Common Hydrocarbon Monomers

9. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Some Common PolymersCC
C
N
H
HH
Polyacrylonitrile(PAN)CC
H
HH
X CC
H
H X
H
Vinyl polymers(one or more H’s of ethylene can be substituted)
Common backbone with substitutions

10. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Monomer-based naming:
poly________
e.g. ethylene -> polyethylene
if monomer name contains more than one word:
poly(_____ ____)
e.g. acrylic acid -> poly(acrylic acid)
Monomer name goes here
Monomer name in parentheses
Note: this may lead to polymers with different names but same structure.CCCC
H
H
H
H
H
H
H
H
……CCCC
H
H
H
H
H
H
H
H ……
polyethylene polymethylene
Nomenclature

11. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Polymerization Methods
H H
A.Free Radical Polymerization
1.Initiation
Free radical initiator
(unpaired electron)CC
H
H H
H
monomerCC

H
HH
R
H R

Radical
transferred
CC
H
H
sbonds
pbond
R
H
H
C
H
H
C
R
sp
2
carbons
sp
3
carbon

12. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Polymerization Methods
A.Free Radical Polymerization
2. PropagationCC
H
H H
H CC

H
HH
R
H CC

H
HH
C
H
H
H
C
H
H
R CC
H
H H
H CC

H
HH
C
H
H
H
C
H
H
C
H
H
C
H
H
R
H
H
C
H
H
C
R
H H
CC
H
H
Both carbon atoms will
change from sp
2
to sp
3
.

13. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Polymerization Methods
A.Free Radical Polymerization
3. TerminationCC

H
HH
R
H CC

H
HH
R
H R

+CC
H
HH
R
H
R CC

H
HH
R
H
+C
H
H
C
H
H
C
H
H
C
H
H
R R
Intentional or unintentional molecules/impurities can also terminate.

14. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Polymerization Methods
B. Stepwise polymerizationR
C
OH
O
NH
2
+R
C
OH
O
NH
2 R
C
N
H
O
NH
2
R
C
OH
O
C. Other methods
Anionic polymerization, cationic
polymerization, coordination
polymerization…R
C
O
N
H
nH
O
H
+H
O
H
+ (n-1)
Loses water
(condensation)
Proteins (polypeptides have similar composition)C
HC
O
N
H
R
n
Various R groups…

15. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Molecular Weights
Not only are there different structures (molecular arrangements)
…… but there can also be a distribution of molecular weights
(i.e. number of monomers per polymer molecule).
20 mers
16 mers
10 mers
Average molecular weight =monomermonomer MM 3.15
3
101620


This is what is called numberaverage molecular weight.

16. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Numberaverage molecular weight:

M
n

N
jM
j
j

N
j
j



m
oN
jj
j

N
j
j


N
j
M
j
j
 
Note: Total weight

N
j
j

Total # of polymer chains
Weightaverage molecular weight:

M
w
W
jM
j
j

W
j
j


N
jM
j
2
j

N
jM
j
j


W
jN
jM
j
In general:

M
N
jM
j
1
j

N
jM
j

j


M
n
If = 0 then If = 1 then

M
w
N
j= # of polymer chains with length j
M
j= jm
o mass of polymer chain with length j
(m
o= monomer molecular weight).

17. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Molecular Weight: Different Notations

M
n

N
jM
j
j

N
j
j


M
n
x
i
M
i
i


x
i

N
i
N
j
j


M
w
N
jM
j
2
j

N
jM
j
j


M
w
w
i
M
i
i


w
i

N
i
M
i
N
j
M
j
j

In Lecture Notes In Callister Textbook

18. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Examples –
Light scattering: larger molecules scatter more light than smaller ones.
Infrared absorption properties: larger molecules have more side
groups and light absorption (due to vibrational modes of side groups)
varies linearly with number of side groups.
Molecular Weights
Why do we care about weight average MW?
-some properties are dependent on MW (larger MW polymer chains can
contribute to overall properties more than smaller ones).
Distribution of
polymer weights

19. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Polydispersity and Degree of Polymerization
Polydispersity:

M
w
M
n
1
When polydispersity = 1, system is monodisperse.
Degree of Polymerization:

n
n

M
n
m
o
Number avg degree of polymerization

n
w

M
w
m
o
Weight avg degree of polymerization

20. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Compute the number-average degree of polymerization for polypropylene,
given that the number-average molecular weight is 1,000,000 g/mol.
What is “mer” of PP?
Mer molecular weight of PP is
Example 1
C
3H
6
m
o=3A
C+6A
H
=3(12.01 g/mol)+6(1.008 g/mol)
= 42.08 g/mol
Number avg degree of polymerization

n
n
M
n
m
o

10
6
g/mol
42.08g/mol
23,700

21. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Example 2 (a, b, and c)
A. Calculate the number and weight average degrees of polymerization
and polydispersityfor a polymer sample with the following distribution.
Avg # of monomers/chain Relative abundance
10 5
100 25
500 50
1000 30
5000 10
50,000 5n
n
M
n
m
o

m
0
m
0
jN
j
j
N
j
j

jN
j
j
N
j
j

5*1025*10050*50030*100010*50005*50000
5255030105
2860.4 n
w
M
w
m
o

1
m
o
(jm
o)
2
N
j
j
N
j(jm
o)
j

j
2
N
j
j
jN
j
j

5*10
2
25*100
2
50*500
2
30*1000
2
10*5000
2
5*50000
2
5*1025*10050*50030*100010*50005*50000
35,800
Note: m
0cancels in all these!

22. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Example 2 (cont.)
B. If the polymer is PMMA, calculate number and weight average
molecular weights.
M
wif monomer is methylmethacrylate (5C, 2O, and 8H)
So m
0= 5(12)+2(16)+8(1)= 100 g/mol
CH3
|
-CH2-C-
|
CO2CH3

M
nn
nm
o2860.4(100g/mol)286,040g/mol
M
wn
wm
o35,800(100g/mol)3,580,000g/mol

M
w
M
n

3,580,000
286,040
~12.52
Polydispersity:

23. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Example 2 (cont.)
C. If we add polymer chains with avg # of monomers = 10such that their
relative abundance changes from 5 to 10, what are the new number
and weight average degrees of polymerization and polydispersity?
Add 5 more monomers of length 10 …. n
n=
M
n
m
o
=
jN
j
j
N
j
j
=
10*10+25*100+50*500+30*1000+10*5000+5*50000
10+25+50+30+10+5
=2750 M
w
M
n
=
3,580,000
275000
~13
Polydispersity:

n
w

M
w
m
o

j
2
N
jj

jN
jj

35,800
Note: significant change in number average (3.8 %)
but no change in weight average!

24. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
For an asymmetric monomer
T H T H+
T HT H
T HH T
H TT HC
H
F
C
H
H
C
F
H
C
H
H
C
H
F
C
H
H
C
H
H
C
F
H
e.g. poly(vinyl fluoride):
H to T T to T
H to H
Random arrangement
e.g. PMMAC
C
CH
3
C
H
H
C
C
CH
3
C
H
H
O
O
CH
3 O
CH
3
O
C
C
CH
3
C
H
H
C
C
CH
3
C
H
H
O
O
CH
3
O
CH
3
O
H to T H to T
H to T
Exclusive H to T arrangement (Why?)
Sequence isomerism

25. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Regularity and symmetry of side groups affect properties
• Stereoisomerism: (can add geometric isomerism too)
Polymer Molecular Configurations
Isotactic
On one side
Syndiotactic
Alternating sides
Atactic
Randomly placed
-Conversion from one stereoisomerism to another is notpossible by simple
rotation about single chain bond; bonds must be severed first, then reformed!
Polymerize
Can it crystallize?
Melting T?

26. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Regularity and symmetry of side groups affect properties
Polymer Geometrical Isomerism
cis-structure trans-structure
with R= CH
3 to form rubber
Cis-polyisoprene trans-polyisoprene
HH
-Conversion from one isomerismto another is notpossible by simple
rotation about chain bond because double-bond is too rigid!
-See Figure 4.8 for taxonomy of polymer structures

27. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Polymer Structural Isomerism
Some polymers contain monomers with more than 1 reactive site
e.g. isopreneCH
2
C
C
H
CH
2
CH
3
trans-isoprene
trans-1,4-polyisopreneC
H
2
C
C
H
C
H
2
CH
3
1
42
trans-1,2-polyisoprene
nC
H
2
C
CH
CH
2
CH
3
n
3
3,4-polyisopreneC
H
2
C
H
C
CH
2
CH
3
n
Note: there are also cis-1,4-and cis-1,2-polyisoprene

28. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Covalent chainconfigurations and strength:
Direction of increasing strength
Adapted from Fig. 14.7, Callister 6e.
Polymer Microstructure
Van der Waals, H
More rigid
Short branching
Long branching
Star branching Dendrimers

29. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Random, Alternating, Blocked, and Grafted
CoPolymers
• Synthetic rubbers are often copolymers.
e.g., automobile tires (SBR)
Styrene-Butadiene Rubber random polymer

30. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Molecular Structure
How do crosslinkingand branchingoccur in polymerization?
1. Start with or add in monomers that have more than 2 sites that bond
with other monomers, e.g. crosslinking polystyrene with divinyl benzene
…
…
stryene polystyrene
Control degree of
crosslinking by
styrene-divinyl
benzene ratio
+
…
…
styrene
divinyl benzene crosslinked polystyrene
Monomers with trifunctional groups lead to network polymers.

31. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Molecular Structure
Branching in polyethylene (back-biting)CH
2
CH
2 R
C
H
2
C
H
2
C
H
2
C
H
2
C
H
2
C

H
H R
C
C
H
2
CH
2
CH
2
C

H
H
H
H
Same as
Radical moves to a different carbon
(H transfer)R
C

C
H
2
CH
2
CH
2
C
H
H
H
H
Polymerization continues from this carbon
Process is difficult to avoid and leads to (highly branched) low-density PE.
When there is small degree of branching you get high-density PE.

32. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Example 3
Nitrile rubber copolymer, co-poly(acrylonitrile-butadiene), has
Calculate the ratio of (# of acrylonitrile)to(# of butadiene).

M
n106,740g/mol

n
n
2000
3 C = 3 x 12.01 g/mol
3 H = 3 x 1.008 g/mol
1 N = 1 x 14.007 g/mol
m
0= 53.06 g/mol
4 C = 4 x 12.01 g/mol
6 H = 6 x 1.008 g/mol
m
0= 54.09 g/mol
1,4-addition product

m
o

M
n
n
n

106,740
2000
53.57g/mol
We need to use an
avg. monomer MW:

m
o
f
1
m
1
f
2
m
2
f
1
(m
1
m
2
)m
2

f
1

m
0
m
2
m
1
m
2

53.3754.09
53.0654.09
0.7

f
2
1f
1
0.3

f
2
f
1

0.7
0.3
7:3

33. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Crosslinking in elastomers is called vulcanization, and is achieved by
irreversible chemical reaction, usually requiring high temperatures.
Vulcanization
• Sulfur compoundsare added to form chains that bond adjacent
polymer backbone chains and crosslinksthem.
•Unvulcnaized rubber is soft and tacky an poorly resistant to wear.
e.g., cis-isoprene
Stress-strain curves
+ (m+n) S
(S)
n
(S)
m
Single bonds
Double bonds
See also sect. in Chpt. 8

34. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Molecular weight, Mw:Mass of a mole of chains.
• Tensile strength (TS):
--often increases with Mw.
--Why? Longer chains are entangled (anchored) better.
• % Crystallinity:% of material that is crystalline.
--TS and E often increase
with % crystallinity.
--Annealing causes
crystalline regions to grow.
% crystallinity increases.crystalline
region
amorphous
region
Adapted from Fig. 14.11, Callister 6e.
Molecular Weight and Crystallinity

35. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Polymer Crystallinity
polyethylene
•Some are amorphous.
•Some are partially crystalline (semi-crystalline).
•Why is it difficult to have a 100% crystalline polymer?%crystallinity

c
(
s

a
)

s
(
c

a
)
100%

s= density of specimen in question

a= density of totally amorphous polymer

c= density of totally crystalline polymer

36. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08

%crystallinity
M
crystalline
M
total
100%

c
V
c

s
V
s
100%

c

s
f
c
100%
Volume fraction of crystalline component.

M
total
M
crystalline
M
amophous
M
s
M
c
M
a

sV
s
cV
c
aV
a

s
c
V
c
V
s

a
V
a
V
s

cf
c
af
a
cf
c
a(1f
c)f
c(
c
a)
a
Using definition of volume fractions:

f
c

V
c
V
s

f
a

V
a
V
s

f
c


s

a

c

a
Substituting in f
cinto the original definition:%crystallinity

c
(
s

a
)

s
(
c

a
)
100%

37. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Polymer Crystallinity
Degree of crystallinity depends on processing conditions (e.g.
cooling rate) and chain configuration.
Cooling rate: during crystallization upon cooling through MP,
polymers become highly viscous. Requires sufficient time for
random & entangled chains to become ordered in viscous liquid.
Chemical groups and chain configuration:
More Crystalline
Smaller/simper side groups
Linear
Isotactic or syndiotactic
Less Crystalline
Larger/complex side groups
Highly branched
Crosslinked, network
Random

38. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Semi-Crystalline Polymers
Fringed micelle model: crystalline region embedded in amorphous region.
A single chain of polymer may pass through several crystalline regions as
well as intervening amorphous regions.

f
c


s

a

c

a
Crystalline volume fractions Important

39. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Semi-Crystalline Polymers
Chain-folded model: regularly shaped platelets (~10 –20 nm thick)
sometimes forming multilayers.
Average chain length >> platelet thickness.

40. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Semi-Crystalline Polymers
Spherulites: Spherical shape composed of aggregates of chain-folded crystallites.
Natural rubber
Cross-polarized light through
spherulite structure of PE.

41. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Diblock copolymers
Representative polymer-polymer
phase behavior with different
architectures:
A) Phase separation with mixed
LINEAR homopolymers.
B) Mixed LINEAR homopolymersand
DIBLOCK copolymergives
surfactant-like stabilized state.
C) Covalent bond between blocks in
DIBLOCK copolymergive
microphase segregation.
F. Bates, Science 1991.

42. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Thermoplastics:
--little cross linking
--ductile
--soften w/heating
--polyethylene (#2)
polypropylene (#5)
polycarbonate
polystyrene (#6)
• Thermosets:
--large cross linking (10 to 50% of mers)
--hard and brittle
--do NOT soften w/heating
--vulcanized rubber, epoxies,
polyester resin, phenolic resinCallister,
Fig. 16.9
T
Molecular weight
Tg
Tm
mobile
liquid
viscous
liquid
rubber
tough
plastic
partially
crystalline
solid
crystalline
solid
Adapted from Fig. 15.18, Callister 6e.
Thermoplastics vs Thermosets
T
m:melting over wide range of T
depends upon history of sample
consequence of lamellar structure
thicker lamellae, higher T
m.
T
g:from rubbery to rigid as T lowers

43. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
•Packing of “spherical” atoms as in ionic and metallic crystals led to
crystalline structures.
•How polymers pack depend on many factors:
•long or short, e.g. long (-CH
2-)
n.
•stiff or flexible, e.g. bendy C-C sp
3
.
•smooth or lumpy, e.g., HDPE.
•regular or random
•single or branched
•slippery or sticky, e.g. C-H covalent (nonpolar) joined via vdW.
Analogy:Consider dried (uncooked) spaghetti (crystalline) vs.
cooked and buttered spaghetti (amorphous).
•pile of long “stiff” spaghetti forms a random arrangement.
•cut into short pieces and they align easily.
Candle wax more crystalline than PE, even though same chemical
nature.
Packing of Polymers

44. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Would you expect melting of nylon 6,6to be lower than PE?
What Are Expected Properties? 

N
|
H

H
|
C
|
H
















6

N
|
H

O
||
C

H
|
C
|
H
















4

N
|
H

O
||
C
 

N
|
H

H
|
C
|
H
















6

N
|
H

O
||
C

H
|
C
|
H
















4

N
|
H

O
||
C

+
+
+
+
+
+

H
C
H

H
C
H
 

H
C
H

H
C
H

+
+
+
+
+
+
nylon 6,6 polyethylene
a)What is the source of intermolecular cohesion in Nylon vs PE?
b)How does the source of linking affect temperature?
Hydrogen bonds
Van der Waals bonds
With H-bonds vs vdW bonds, nylon is expected to have (and does) higher melting T.

45. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Which polymer more likely to crystallize? Can it be decided?
What Are Expected Properties?
Linear syndiotactic polyvinyl chlorideLinear isotactic polystyrene
•Linear and syndiotactic polyvinyl chloride is more likely to crystallize.
•The phenyl side-group for PS is bulkier than the Cl side-group for PVC.
•Generally, syndiotactic and isotactic isomers are equally likely to crystallize.
•For linear polymers, crystallization is more easily accomplished as chain
alignment is not prevented.
•Crystallization is not favored for polymers that are composed of
chemically complex mer structures, e.g. polyisoprene.

46. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Which polymer more likely to crystallize? Can it be decided?
What Are Expected Properties?
Linear and highly crosslink
cis-isoprene
•Not possible to decide which might crystallize. Both not likely to do so.
•Networked and highly crosslinked structures are near impossible to
reorient to favorable alignment.
H
+
+ H
20
Networked
Phenol-Formaldehyde
(Bakelite)

47. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Which polymer more likely to crystallize? Can it be decided?
What Are Expected Properties?
alternating
Poly(Polystyrene-Ethylene)
Copolymer
random
poly(vinyl chloride-tetra-fluoroethylne)
copolymer
•Alternating co-polymer more likely to crystallize than random ones, as they are
always more easily crystallized as the chains can align more easily.

48. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
•Soap is a detergent based on animal or vegetable product, some
contain petrochemicals
Detergents
grease
water
detergent
•What properties of soap molecules do you need to remove grease?
•“green” end must be “hydrophilic”. Why?
•Opposite end must be hydrocarbon. Why?
Water must be like oxygen(hoard
electrons and promote H-bonding)
greasee.g., oxy-clean®

49. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Simple polymer: Elmers glue + Borax SLIME!
Chemistry Elmer’s glueis similar to “poly (vinyl alcohol)” with formula:
Borax is sodium tetraborate decahydrate (B
4Na
2O
7• 10 H
2O).
The borax actually dissolves to form boric acid, B(OH)
3.
This boric acid-borate solution is a buffer with a pH of about 9 (basic).
Boric acid will accept a hydroxide OH-from water.
B(OH)
3+ 2H
2O B(OH)
4
-
+ H
3O
+
pH=9.2
OHOHOHOHOHOHOHOHOHOHOHOHOHOHOH
this is a SHORT, n=15chain of poly(vinyl alcohol)
Hydrolyzed molecule acts in a condensation reaction
with PVA, crosslinkingit.

50. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Simple polymer: Elmer’s glue + Borax SLIME!
Hydrolyzed molecule acts in a condensation reaction with PVA,
crosslinkingit.
B(OH)
3+ 2H
2O B(OH)
4
-
+ H
3O
+
pH=9.2

Crosslinkingties chains via weak non-covalent
(hydrogen) bonds, so it flows slowly.
Crosslinked

51. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
Range of Bonding and Elastic Properties
Is “slime” a thermoset or thermoplastic, or neither?
Thermoset
bonding
Thermoplastic
bonding
•Induced dipolar bonds
form crosslinks
Slime?
Stiffness increases
Where is nylon?
•Covalent bonds form
crosslinks •H-bonds form
crosslinks

52. MatSE 280: Introduction to Engineering Materials ©D.D. Johnson 2004, 2006, 2007-08
• Polymers are part crystallineand part amorphous.
•The more “lumpy” and branchedthe polymer, the less dense
and less crystalline.
•The more crosslinkingthe stifferthe polymer. And, networked
polymers are like heavily crosslinked ones.
•Many long-chained polymers crystallize with a Spherulite
microstructure-radial crystallites separated by amorphous
regions.
•Optical properties: crystalline -> scatter light (Bragg)
amorphous -> transparent.
Most covalent molecules absorb light outside visible spectrum, e.g.
PMMA (lucite) is a high clarity tranparent materials.
Summary