Transcript Slide 1

European Plastic Welder
Chapter 1: Plastics
Co – ASR, Romanian Welding Society
P1 – CWS, Czech Welding Society ANB
P2 – SLV, Schweisstechnische Lehr- und Versuchsanstalt SLV Duisvurg, Niederlassung der GSI mbH
P3 – IIS, Italian Welding Institute
P4 – EWF, European Federation for Welding, Joining and Cutting
P5 – ISQ, Institute for Welding and Quality
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1.1
Generals on Polymers
Definitions
Application of polymers
Nomenclature of polymers
Classification of polymers
Main physical properties of polymers
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Introduction to polymers
Term “polymer”: greek poli (many) + meros (unit) = many units
Polymers are a large class of materials
consisting of many small molecules
(called monomers) that can be linked
together to form long chains, thus they are
known as macromolecules (term
introduced by H. Staudinger in 1920’s).
A typical polymer may include tens of
thousands of monomers. Because of their
large size, polymers are classified as
macromolecules.
Polymers occur naturally in the form of
proteins, cellulose(plants), starch(food)
and natural rubber.
Engineering polymers, however, are
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Definitions
Polymer
Large molecule consisting of a number of repeating units with molecular
weight typically several thousand or higher
Repeating unit
The fundamental recurring unit of a polymer
Monomer
The smaller molecule(s) that are used to prepare a polymer
Oligomer
A molecule consisting of reaction of several repeat units of a monomer but
not large enough to be consider a polymer
Single repeat unit: MONOMER
Many repeat units: POLYMER
Degree of polymerization
The number of the repeating units
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Application of polymers
The field of synthetic polymers or
plastics is currently one of the fastest
growing materials industries. The
interest in engineering polymers is
driven by their manufacturability,
recyclability, mechanical properties,
and lower cost as compared to many
alloys and ceramics.
Also the macromolecular structure of
synthetic polymers provides good
biocompatibility and allows them to
perform many biomimetic tasks that
cannot be performed by other
synthetic materials, which include
drug delivery, use as grafts for
arteries and veins and use in artificial
tendons, ligaments and joints.
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Application of polymers
INCPEN, Towards greener households, June 2001
p. 580.0400 A of the Chemical Economics Handbook
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Application of polymers
ACCENTURE RESEARCH, Trends in Manufacturing Polymers: Achieving High Performance in a Multi-Polar World, www.accenture.com
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Nomenclature of polymer
1- Nomenclature Based on monomer source
The addition polymer is often named according to the monomer that was
used to form it
Example : poly( vinyl chloride ) PVC is made from vinyl chloride
-CH2-CH(Cl)If “ X “ is a single word the name of polymer is written out
directly
ex. polystyrene
-CH2-CH(Ph)Poly-X
If “ X “ consists of two or more words parentheses should be
used
ex , poly (vinyl acetate ) -CH2-CH(OCOCH3)-
2- Based on polymer structure
The most common method for condensation polymers since the polymer
contains different functional groups than the monomer
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Nomenclature of polymers
PC =
Polycarbonat
PPE =
Polyphenylether
SMA =
Styrol-Maleinsäureanhydrid
ABS =
Acrylnitril-Butadien-Styrol
PMMA = Polymethylmethacrylat
PS =
Polystyrol
SAN =
Styrol-Acrylnitril-Copolymere
PVC =
Polyvinylchlorid
PET = Polyethylenterephthalat (PETP)
PBT = Polybutylenterephthalat (PBTP)
PA =
Polyamid
POM = Polyoxymethylen
RF-PP = Resorcin-Formaldehyd-Polypropylen
PE-UHMW = Polyethylen-ultra high molecular weight
PP =
Polypropylen
PE-HD = Polyethylen hoher Dichte (High Density)
PE-LD = Polyethylen niedriger Dichte (Low Density)
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Classification of polymers
Main classifications of the polymers:
• by origin
• by Monomer composition
• by chain structure
• by thermal behaviour
• by kynetics or mechanism
• by application
A. Classification by Origin
 Synthetic organic polymers
Biopolymers (proteins, polypeptides, polynucleotide, polysaccharides, natural
rubber)
Semi-synthetic polymers (chemically modified synthetic polymers)
Inorganic polymers (siloxanes, silanes, phosphazenes)
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B. Classification by Monomer Composition
 Homopolymers
 Copolymers
 Block
Graft
Alternating
Statistical
Homopolymers
Consist of only one type of constitutional repeating unit (A)
AAAAAAAAAAAAAAA
Homopolymer
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Copolymers
Consist of two or more constitutional repeating units (A-B )
Several classes of copolymer are possible
 Statistical copolymer (Random)
ABAABABBBAABAABB
two or more different repeating unit
are distributed randomly
 Alternating copolymer
ABABABABABABABAB
are made of alternating sequences
of the different monomers
 Block copolymer
AAAAAAAAABBBBBBBBB
long sequences of a monomer are followed
by long sequences of another monomer
 Graft copolymer
AAAAAAAAAAAAAAAAAA
B
B
B
B
B
B
Consist of a chain made from one type of
monomers with branches of another type
Statistical
Alternating
Block
Graft
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c. Classification by Chain structure (molecular architecture)
 Linear chains :a polymer consisting of a single continuous chain of repeat units
 Branched chains :a polymer that includes side chains of repeat units connecting
onto the main chain of repeat units
 Hyper branched polymer consist of a constitutional repeating unit including a
branching groups
 Cross linked polymer :a polymer that includes interconnections between chains
 Net work polymer :a cross linked polymer that includes numerous
interconnections between chains
Linear
Branched
Cross-linked
Network
Direction of increasing strength
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d. Classification by Thermal Behavior
Polymers may be classified as follows, according to the mechanical response at
elevated temperatures:
•
Thermoplasts
•
Thermosets.
a) Thermoplasts:
Thermoset polymers soften when heated and harden when cooled. Simultaneous
application of heat and pressure is required to fabricate these materials.
On the molecular level, when the temperature is raised, secondary bonding forces
are diminished so that the relative movement of adjacent chains is facilitated
when a stress is applied.
Most Linear polymers and those having branched structures with flexible chains are
thermoplastics.
Thermoplastics are very soft and ductile.
The commercial available thermoplasts are
•
Polyvinyl Chloride (PVC) and Polystyrene
•
Polymethyl methacrylate
•
Polystyrene
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Classification by Thermal Behavior
b) Thermosets:
Thermosetting polymers become soft during their first heating and become
permanently hard when cooled. They do not soften during subsequent heating.
Hence, they cannot be remolded/reshaped by subsequent heating.
In thermosets, during the initial heating, covalent cross-links are formed between
adjacent molecular chain. These bonds anchor the chains together to resist the
vibration and rotational chain motions at high temperatures. Cross linking is
usually extensive in that 10 to 15% of the chain mer units are cross linked. Only
heating to excessive temperatures will cause severance of these crosslink
bonds and polymer degradation. Thermoset polymers are harder, stronger,
more brittle than thermoplastics and have better dimensional stability.
They are more usable in processes requiring high temperatures
Most of the cross linked and network polymers which include
• Vulcanized rubbers
•
•
•
Epoxies
Phenolic
Polyester resins
are thermosetting polymers.
Thermosets cannot be recycled, do not melt, are usable at higher temperatures
than thermoplastics, and are more chemically inert
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e. Classification Based on Kinetics or Mechanism
 Step-growth
 Chain-growth
f. Classification by Application
 Plastics
 Fibers
 Elastomers
 Coatings
 Adhesives
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Main physical properties of polymers
1-Primary bonds : the covalent bonds that
connect the atoms of the main chain
2- Secondary bonds : non – covalent bonds
that hold one polymer chain to
another including hydrogen bond and other
dipole –dipole attraction
3-Crystalline polymer : solid polymers with
high degree of structural order and rigidity
4- Amorphous polymers : polymers with a low
degree of structural order
5-Semi – crystalline polymer : most polymers
actually consist of both
crystalline domains and amorphous domains
with properties between that
expected for a purely crystalline or purely
amorphous polymer
6-Glass: the solid form of an amorphous
polymer characterized by rigidity and
brittleness
7 – Crystalline melting temperature (Tm):
temperature at which crystalline polymers melt
8 - Glass transition temperature (Tg ) :
temperature at which an amorphous
polymer converts to a liquid or amorphous
domains of a semi crystalline polymer melt
9 – Thermoplastics (plastics ) :polymers
that undergo thermally reversible
Interconversion between the solid state and
the liquid state
10- Thermosets : polymers that continue
reacted at elevated temperatures
generating increasing number of crosslinks
such polymers do not exhibit
melting or glass transition
11- Liquid – crystalline polymers : polymers
with a fluid phase that retains
some order
12- Elastomers : rubbery , stretchy
polymers the effect is caused by light
crosslinking that pulls the chains back to
their original state
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Amorphous
Crystalline
Glass phase (hard plastic)
9
8
7
Log (stiffness)
6
Pa
Leathery phase
Rubber phase (elastomer)
5
4
Liquid
3
Temperature
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1.2
Polymers in the Solid State
Glass Transition Temperature
Crystalline Structure
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POLYMERS IN THE SOLID STATE
Amorphous
Semi-crystalline
Glassy
Rubbery
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Glass Transition Temperature
• The glass transition, Tg, is temp. below
which a polymer OR glass is brittle or
glass-like; above that temperature the
material is more plastic.
•The Tg to a first approximation is a
measure of the strength of the secondary
bonds between chains in a polymer; the
stronger the secondary bonds; the
higher the glass transition temperature.
Polyethylene Tg = 0°C;
Polystyrene = 97 °C
PMMA (plexiglass) = 105 °C.
Since room temp. is < Tg for PMMA, it is
brittle at room temp.
For rubber bands: Tg = - 73°C….
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Crystallinity
Crystallization in linear polymers: achieving a very regular arrangement
of the mers
Induction of crystallinity
● cooling of molten polymer
● evaporation of polymer solution
● annealing  heating of polymer at a specific temperature
● drawing  stretching at a temperature above Tg
Effects:





Increased Density
Increases Stiffness (modulus)
Reduces permeability
Increases chemical resistance
Reduces toughness
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Crystalline polymers (vs amorphous polymers)
 tougher, stiffer (due to stronger
interactions)
 higher density, higher solvent
resistance (due to closely packing
morphology)
 more opaque (due to light
scattering by crystallites)
Crystalline morphologies
• Spherulite  aggregates of small fibrils in a radial pattern (crystallization
under no stress)
• Drawn fibrillar  obtained by drawing the spherulitic fibrils
• Epitaxial  one crystallite grown on another; lamella growth on long
fibrils; the so-called shish-kebab morphology (crystallization under
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1.3
Characteristics of polymers.
Behaviour in exploitation
Maximum service temperature
Coefficient of friction
Flammability
Tensile strengh at break
Coefficient of linear expansion
Thermal guidelines
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1.4
Polyethylene
Principal Olefin Monomers
Mechanical Properties of Polyethylene
Physical Properties of Polyethylene
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Principal Olefin Monomers
• Ethylene
H
H
C
C
H
H
Poly
n
H
• Butene-1
Poly
• Propylene
C
C2H5
H
• 4-Methylpentene
n
H
C
C
CH3
H
Poly
H
C
H
Poly
n
H
H
C
C
C5H6
H
CH3
n
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Mechanical Properties of Polyethylene
•
•
•
•
Type 1: (Branched) Low Density of 0.910 - 0.925 g/cc
Type 2: Medium Density of 0.926 - 0.940 g/cc
Type 3: High Density of 0.941 - 0.959 g/cc
Type 4: (Linear) High Density to ultra high density > 0.959
Mechanical Properties
Branched Low
Density
Density
0.91- 0.925
Medium
Density
0.926- 0.94
High
Density
0.941-0.95
Linear High Density
0.959-0.965
Crystallinity
30% to 50%
50% to 70%
70% to 80%
80% to 91%
Molecular
Weight
Tensile
Strength, psi
Tensile
Modulus, psi
Tensile
Elongation, %
Impact Strength
10K to 30K
30K to 50K
50K to 250K
250K to 1.5M
600 - 2,300
1,200 - 3,000
3,100 - 5,500
5,000 – 6,000
25K – 41K
38K – 75 K
150K – 158 K
100% - 650%
100%- 965%
150K – 158
K
10% - 1300%
No break
1.0 – no
break
D50 – D60
0.4 – 4.0
0.4 – 4.0
D60 – D70
D66 – D73
ft-lb/in
Hardness, Shore D44 – D50
10% - 1300%
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Physical Properties of Polyethylene
Physical Properties of polyethylene
Branched Low Medium Density
Density
Optical
Transparent to Transparent to
opaque
opaque
Tmelt
98 – 115 C
122 – 124 C
High
Density
Transparent to
opaque
130 – 137 C
Linear High Density
Transparent to opaque
130 –137 C
Tg
-100 C
H20 Absorption Low < 0.01
-100 C
Low < 0.01
-100 C
Low < 0.01
-100 C
Low < 0.01
Oxidation
Resistance
UV Resistance
Low, oxides
readily
Low, Crazes
readily
Resistant
below 60C
Resistant
Low, oxides
readily
Low, Crazes
readily
Resistant below
60C
Resistant
Low, oxides readily
Low, oxides readily
Low, Crazes readily
Low, Crazes readily
Resistant below 60C
Resistant below 60C
Resistant
Resistant
Oxidizing
Acids
Oxidizing Acids
Oxidizing Acids
Oxidizing Acids
Solvent
Resistance
Alkaline
Resistance
Acid
Resistance
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1.5
Polypropylene
Polypropylene Structure
Advantages/Disadvatages of Polypropylene
Mechanical Properties of Polypropylene
Physical Properties of Polypropylene
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Polypropylene Structure
• Propylene
H
H
C
C
CH3
H
• Isotactic- CH3 on one side of polymer chain (isolated).
Commercial PP is 90% to 95% Isotactic
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
C
C
CH3 H
CH3 H
CH3 H
CH3 H
CH3 H
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Advantages/Disadvatages of Polypropylene
• Advantages
– Low Cost
– Excellent flexural strength
– Good impact strength
– Processable by all
thermoplastic equipment
– Low coefficient of friction
– Excellent electrical insulation
– Good fatigue resistance
– Excellent moisture resistance
– Service Temperature to 126oC
– Very good chemical resistance
• Disadvantages
– High thermal expansion
– UV degradation
– Poor weathering resistance
– Subject to attack by
chlorinated solvents and
aromatics
– Difficulty to bond or paint
– Oxidizes readily
– flammable
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Mechanical Properties of Polypropylene
Mechanical Properties of Polypropylene
HDPE
Polypropylene LDPE
(For Comparison) (For Comparison)
0.90
0.91- 0.925
0.959-0.965
Density
Crystallinity
30% to 50%
30% to 50%
80% to 91%
Molecular Weight
200K to 600K
10K to 30K
250K to 1.5M
Molecular Weight
Dispersity MWD
(Mw/Mn)
Tensile Strength,
psi
Tensile Modulus,
psi
Tensile
Elongation, %
Impact Strength
Range of
MWD for
processing
4,500 – 5,500
Range of MWD
for processing
Range of MWD
for processing
600 - 2,300
5,000 – 6,000
165K – 225K
25K – 41K
150K – 158 K
100% - 600%
100% - 650%
10% - 1300%
0.4 – 1.2
No break
0.4 – 4.0
R80 - 102
D44 – D50
D66 – D73
ft-lb/in
Hardness, Shore
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Physical Properties of Polypropylene-Polyethylene
Physical Properties of Polypropylene
HDPE
Polypropylene LDPE
Transparent to Transparent to
Transparent to opaque
Optical
opaque
opaque
175 C
98 – 115 C
130 –137 C
Tmelt
Tg
H20
Absorption
-20 C
0.01 – 0.03
Low, oxides
Oxidation
readily
Resistance
UV Resistance Low, Crazes
readily
Resistant
Solvent
below 80C
Resistance
Resistant
Alkaline
Resistance
Oxidizing
Acid
Acids
Resistance
-100 C
Low < 0.01
-100 C
Low < 0.01
Low, oxides
readily
Low, Crazes
readily
Resistant below
60C
Resistant
Low, oxides readily
Oxidizing Acids
Oxidizing Acids
Low, Crazes readily
Resistant below 60C
Resistant
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Reference
1] Billmeyer, F. W., Textbook of Polymer Science, 3rd ed., Interscience Publishers,
1984 (classic book with excellent treatment of polymer properties)
[2] Barth, H. G. and Mays, J. W., Eds., Modern Methods of Polymer
Characterization, Wiley, 1991 (covers latest developments at the time of most
methods)
[3] Brady, Jr., R. F., Ed., Comprehensive Desk Reference of Polymer
Characterization and Analysis, American Chemical Society-Oxford, 2003 (survey
of characterization and analytical methods)
[4] Brandrup, J., Immergut, E. H. ,Grulke, E. A., Abe, A, and Bloch, D. R., Eds.,
Polymer Handbook, 4th ed., John Wiley and Sons, 2005 (premier handbook of
polymer science, listing virtually all polymer characteristics for most polymers)
[5] Brydson, J. A., Plastics Materials, Butterworth Heinemann, 2000
(comprehensive treatment of plastics, their synthesis, properties, and applications)
[6] Bueche, F., Physical Properties of Polymers, Krieger Publishing, 1979
(emphasis is on polymer physics)
[7] Cowie, J.M.G. and Arrighi, V., Polymers: Chemistry and Physics of Modern
Materials, 3rd ed., CRC Press 2008 (excellent discussion of physical properties
and applications)
[8] Heimenz, P.C. and Lodge, T. P., Polymer Chemistry, 2nd ed., CRC Press, 2007
(comprehensive treatment of polymer chemistry - synthesis and physical
chemistry)
[9] Mark, J.E., Allcock, H. R., and West, R., Inorganic Polymers, Oxford, 2005
(physical chemistry and properties of inorganic polymers)
[10] Mark, J. E., Ed., Polymer Data Handbook, Oxford, 1999 (compilation of major
classes of polymers and their physical properties)
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[11] Mori, S. and Barth, H. G., Size Exclusion Chromatography, SpringerVerlag, 1999 (comprehensive treatment of SEC, theory and applications)
[12] Munk, P. and Aminabhavi, T. M., Introduction to Macromolecular Science,
2nd ed., John Wiley and Sons, 2002 (emphasis on polymer physical chemistry)
[13] Nielsen, L. E., Polymer Rheology, Marcel Dekker, 1977 (introductory text
on polymer rheology)
[14] Richardson, T. L. and Lokensgard, E., Industrial Plastics: Theory and
Applications, Delmar, 1996 (practical overview of some important properties
and polymer processing)
[15] Carraher, Jr., C. E., Seymour/Carraher's Polymer Chemistry, 7th ed., CRC
Press, 2007 (popular introduction to polymer chemistry)
[16] Seymour, R. B., Engineering Polymer Sourcebook, McGraw Hill, 1990
(good overview of physical properties of engineering polymers)
[17] Sperling L. H., Introduction to Physical Polymer Science, 2d d., WileyInterscience, 1992 (good treatment of polymer physics and properties)
[18] van Krevelen, D. W., Properties of Polymers, 3rd ed., Elsevier, 1990 (indepth treatment of polymer properties, best resource available)
[19] Whistler, R., Industrial Gums, 2nd ed., Academic Press, 1973 (although
outdated, gives solid background on the chemistry and properties of cellulosics
and polysaccharides)
[20] Wu, C. S., Ed., Handbook of Size Exclusion Chromatography, 2nd ed.,
Marcel Dekker, 2003 (covers all aspects of this important technique).
[21] Course: Classes of Polymeric Materials, Joe Greene, CSU, CHICO
[22] Course: Engineering Thermoplastics, Joe Greene, CSU, CHICO
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