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7/30/2019 Thermoplastic Engineering
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Thermoplastic Materials
Engineering Plastics
MFG 355
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Engineering Thermoplastics
Replace metallic parts
Strength and stiffness
Retention of properties over range of temperatures
Toughness to withstand incidental damage Dimensional stability
Low creep
Low CTE
Withstand environmental factors (UV, O2, chemicals) Shaped easily
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Engineering Thermoplastics
Compared to commodity plastics
More expensive
The commodity resins are all lacking some
critical property
Some Engineering Thermoplastics are formed
through the condensation polymerization
process
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( )nCN N C C C
O OH HH
H
H
H
[ ]a [ ]b
Polyamides or Nylons (PA)
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PA General Family Characteristics
Polarity
Crystallinity
Sharp meltpoint Strength
Comparison of higher & lower nylon
numbers
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PA General Family Characteristics
Transparent (barely)cook in bag (turkey)
Anti-frictionnot like PTFE but good
Toughness
excellent Fatigue resistanceexcellent
Water absorptiona weakness (.2-2.5%
must be dried for injection molding) Highly crystalline
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Nylon 6,6
C C C C C CNH2 NH2
H
H
H
H
H
H
H
H
H
H
H
H
Hexamethylenediamine
(6 carbons)
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Nylon 6,6
C C C C C C
O
OH O
OHH
H
H
H
H
H
H
H
Adipic Acid
(6 carbons)
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Nylon 6,6
NH
C C C C C C
O OH
OCCCCCCNH2
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
O
H
H
Water
Nylon 6,6
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Nylon 6
C C C C C CNH2
O
OH
H
H
H
H
H
H
H
H
H
H
Amine
Group
Acid
Group
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Nylon 6
C
C
C
C
C
C
NH2
O
H
H
H
H
H
H
H
H
H
H
N
C
C
C
C
C
C
OH
O
H
H
H
H
H
H
H
H
H
H
H
O
H
H
Water
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Properties of Specific Nylon Types
Nylon 6,6 General
Nylon 6 Copycat
Nylon 6,10
Less water absorption Nylon 6,12 Flexibility and less water
Nylon 2,2 Strength
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Processing Nylon
Injection molding Shrinkagecrystallinity.018 in/in
Dry it first
Extrusion Low melt viscosity
Be careful of decomposition
Fibers
Drawing Crystallization
Orientation
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Nylon History
Nature of polymer bonding not understood
Carothers
Difunctional monomers
Polymers1000 units long Larger unitsmolecular still to eliminate water
Control of melting point and length Many combinations of polyesters
Trying polyamides
Settling on 6,6
Carothers death 3 weeks after patents
Tremendous success Name
Delawear, Wacra, Norun, Nuron, Nulon, Nilon, Nylon
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Aramids
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C C
C C
C
CC
C
O O
N C
C C
C
CC
N
H
H
H H
H H
H H
HH
Aramids
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Acetals or Polyoxymethylenes
(POM)
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Acetals or Polyoxymethylenes
(POM)
C O
H
H
( )n
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Acetal General Family
Characteristics Mechanicaldo not embrittle, good impact
strength
Moisturevery little (shower heads)
Chemical resistancevery high, resists stains,sensitive to strong acids and bases
Weatheringfair
Thermal200o F
Electricalgood
Machininglike cutting brass
Adhesionepoxy glues
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Processing Acetals
Do not heat above 440o F
Melt viscosity is not too dependant on
temperature
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Acetal Copolymer
CH2 O
CH2 CH2
O CH2
O
O(
(n
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Thermoplastic Polyesters
(PET/PBT)
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Thermoplastic Polyesters
(PET/PBT)
O C C O C
C C
C C
C C
C
O
H H
H H
H
H
H
H
(
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Thermoplastic Polyester General
Family Characteristics
PET
Higher mechanical stiffness
Strength by orienting chains not by H-bonding
Get 50% crystallinity
forced by mechanical stretching
PBT
crystallizes rapidly
processes faster
lower overall properties
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Processing PET
Shape it (film, tape, fiber, extrude, etc)
Amorphous structure
Reheat and stretch in strength direction(s)
Cool to below Tg
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Specific TP Polyester Types
Dacron fibermix with cotton or wool-gives
permanent creases
Kodel photo film
Mylartransparencies, tapes
PETGglycol modified, amorphous, like PVC
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Polycarbonate
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Polycarbonate
O C O
O
C
C C
C
CC
C
C
C
C
C C
C
CC
H H
H H H
H H
H
H H
H
H
H H
( )n
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History
Solvent resistance (DuPont)
GE-Lexan
Properties Polar
Stiffness of backbone
Long repeat unit
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Properties
Solvent sensitivitypoor but nice for joining Clearexcept for UV yellowing, slight
crystallinity
Hard
Ductilenailed, sawed, drawn, punched,sheared, drilled
Toughhelmets, light covers, windows,roadside signs, bullet proof shields
Dimensional stabilitylow creep Electrical resistancegood but not fantastic
Machininggood
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Acrylics (PAN, PMMA)
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Acrylics (PAN, PMMA)
C
C C
C O
O
C
H
H
H
HH
HH
H
( )n ( )n
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Properties
Color (transparency)20 years w/
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Uses
Signs
Counter topsCorian
Decorative pieces Floor waxes
Paint, fingernail polishes
Contact lenses, glasses
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Processing
Casting (sheets)syrup
Injection moldinggood
Thermoforming
ok but brittle Machiningsimilar to wood
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Flouropolymers (PTFE, FEP, PFA)
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Flouropolymers (PTFE, FEP, PFA)
C C
F F
F F
)n)n(
(
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History of Discovery
Chambers plant
Making Freon
Gas cylinder
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Properties
Most are strengthened by the tight bondbetween the Fluorine and the Carbonatoms
Slippery (anti-stick surfaces)
Chemical inertness
High temperature melting
Non-flammable
High electrical resistance
Very dense2.13-2.2 (high melt viscosity)
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Uses
O-rings
Non-stick surfaces
Insulation-electrical Lubricant
Coatings
Gears
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Processing
Not processable by extrusion or injectionmolding Sintering
Put in approx shape and heat620o F
Similar to processing powdered metals Fusion
Ram extrusion Compaction
Rods and tubes
Calendaring
Very poor adhesion
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High Performance Thermoplastics
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PPO Properties
Thermal stabilityexcellent (650o F)
High HDT = 375o F
Good cold properties (-275
o
F) Low water absorption
Low heat expansion
Good solvent resistance, but can besolvent welded
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PPO uses
Used to replace stainless steel for surgical
equipment
Replace thermosets
Pump housings
Valve components
Video terminal housings
P l l th k t (PEEK PEK
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Polyaryletherketones (PEEK, PEK,
and Others)
P l l th k t (PEEK PEK
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Polyaryletherketones (PEEK, PEK,
and Others)
C
C C
C
CC
O C
C C
C
CC
C
O
C
C C
C
CC
HH
HHHH
HH
HH
HH
Ether
Linkage
Ketone
Linkage
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Polysulfones (PSU and PES)
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Polysulfones (PSU and PES)
C
C C
C
CC
S
O
O
C
C C
C
CC
O C
C C
C
CC
C
C C
C
CC
O
H H
H H H
H H
H H
H H
H H
H H
H
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Properties
Resistant to oils
Heat stability (300o F)
Creep resistance
SO2 group adds stiffness
More dimensionally stable than PPO
Toughness
good
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Uses
Hot water pipes
Coffee pots
Dishwasher components
Automobile applications near engines
Compete with thermosets, but can be
injection molded
Th l ti P l i id (PI d
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Thermoplastic Polyimides (PI and
PAI)
Th l ti P l i id (PI d
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Thermoplastic Polyimides (PI and
PAI)
C
C
C
C
C
C
C
C
N
O
OH
H
H
( )n)n
(
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Properties
Very stiff
Highest thermal stability
PI cannot be melted or melt processed
PAI can be (Torlon)
PI is sintered (Vespel)
PI film is cast as monomers and heated topolymerize (Kapton)
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Uses
PI is used in circuit boards
High temperature parts
Low friction bearings, sliding parts
Gears
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Cellulosics
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Cellulosics
Nitrocellulose
Gun cotton
Cellulose nitrate
Lacquers and plastics
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Fire
Hard
Plasticized with camphor
Water repellent
Fire
Properties
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Types of Cellulosics
Rayon
Viscose process
Cellophane
Methyl cellulose
Filler
Edible
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Thank You
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Nylon History
Carothers
IowaBS
IllinoisPhD
HarvardTeach
DuPontbasic research
Polyphenylenes (PPE PPO and
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Polyphenylenes (PPE, PPO, and
PPS)
C
C
C
C
C
C
C
C
OHH
H
H H
H
H
H
HH
PPO