thermoplastic engineering material

8/14/2019 Thermoplastic Engineering Material

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Thermoplastic Materials

Engineering Plastics BY-LAKHAN SINGH


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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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Polyamides or Nylons (PA)


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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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Nylon History

Carothers

IowaBS

IllinoisPhD

HarvardTeach

DuPontbasic research


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( )n[ ]a [ ]b

Polyamides or Nylons (PA)

[ ]a[ ]b


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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

Toughnessexcellent 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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Aramids


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Aramids


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Acetals or Polyoxymethylenes

(POM)


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Acetals or Polyoxymethylenes

(POM)

( )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 Thermal200oF 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

(

(n


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Thermoplastic Polyesters

(PET/PBT)


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Thermoplastic Polyesters

(PET/PBT)

(

)n


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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

( )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)

( )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

Thermoformingok but brittle Machiningsimilar to wood


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Flouropolymers (PTFE, FEP, PFA)


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Flouropolymers (PTFE, FEP, PFA)

)n)n(

(


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History of Discovery

Chambers plant

Making Freon

Gas cylinder


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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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Polyphenylenes (PPE, PPO, and

PPS)

C

C

C

C

C

C

C

C

OHH

H

H H

H

H

H

HH

PPO


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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)

Ether

Linkage

Ketone

Linkage


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Polysulfones (PSU and PES)


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Polysulfones (PSU and PES)


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Properties

Resistant to oils

Heat stability (300o F)

Creep resistance

SO2 group adds stiffness

More dimensionally stable than PPO

Toughnessgood


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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)

( )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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Thank You

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