Plastic Materials Selection, Slides of Engineering

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Plastic Materials Selection

Jose M. Perez, Jr.

Senior Engineer, Polymers

Element - New Berlin

Introduction

Engineers face several considerations when selectingEngineers

face

several

considerations

when

selecting

the

optimum

polymer

material

for

a

product

• Knowing

full

product

requirements

in

a

wide

range

of

environments

• Thoroughly

understanding

of

the

true

functional

behavior

of the polymerof

the

polymer

• Using

this

knowledge

to

sift

through

an

almost

infinite

number

of

resin/additive

combinations

Plastic Materials Selection

What

is

a

“Polymer”?

“Polymer” is from the Greek “poly” (many)

Polymer

is

from

the

Greek

poly

(many)

and

“meros”

(part)

“Polymers” are

long

organic

molecules

made

up

of

many

small

units

(monomers)

chemically

joined

end

‐to

‐end

Plastic Materials Selection

Common

Mer Structures

Polyethylene

Polybutadiene

o yet y e ePolypropylene

Nylon

6

yp

py

Polyvinyl

chloride

Polycarbonate

Polystyrene

Polyethylene

terephthalate

PolystyrenePolytetrafluoroethylene

y^

y

Examples

Thermoplastic

Thermoset

p

•^

Polypropylene

(PP)

•^

Polyamide

(PA,

a.k.a Nylon)

•^

Phenolic (PF)

-^

Epoxy

(EP)

•^

Polycarbonate

(PC)

•^

Acrylonitrile

butadiene

styrene

(ABS)

•^

Unsaturated

polyester

(UP)

•^

Polyurethane

(PUR)

(ABS)

•^

Polyacetal (POM)

-^

Poly(ethylene terephthalate)

•^

Acrylonitrile

butadiene

rubber

(NBR)

•^

Ethylene propylene

diene

•^

Poly(ethylene

terephthalate

(PET)

•^

Ethylene

propylene

‐diene

monomer

(EPDM)

rubber

Plastic Materials Selection

Thermoplastic

Types

Amorphous

lacking long range order

Amorphous

lacking

long

range

order

Semi

‐crystalline

polymers

possessing

long

range

molecular

order^ Plastic Materials Selection

General

Traits

Amorphous materials can be characterized by theirAmorphous

materials

can

be

characterized

by

their

glass

transition

temperature

(Tg)

Glass

transition

temperature

The

temperature

at

which

a

material's

characteristics

change

f

rom

that

g

f

of

a

glass

to

that

of

rubber.

Semi

‐crystalline

materials

can

be

characterized

by

their

Tg and

melting

temperature

(Tm)

Plastic Materials Selection

Thermal

Properties

Material

Tg

[°C

(°F)]

T^ m

[°C

(°F)]

Polyethylene

(low

density)

‐^110

(‐

115

(240)

Polytetrafluoroethylene

‐^97

(‐

327

(620)

Polyethylene

(high

90 (

137 (279)

density)

‐^90

(‐

137

(279)

Polypropylene

‐^18

(0)

175

(347)

Nylon

6,

57

(135)

265

(510)

Polyester

(PET)

69

(155)

265

(510)

Polyvinyl

chloride

87

(190)

212

(415)

Polystyrene

100

(212)

240

(465)

Polycarbonate

150

(300)

265

(510)

Polysulfone

185

(365)

360

(680)

Examples

^

Amorphous•

Polyetherimide (PEI)

^

Semi

‐Crystalline

-^

Polyetheretherketone (PEEK)

-^

Polyetherimide (PEI)

-^

Polyethersulfone (PES)

-^

Polysulfone

(PSU)

-^

Polyetheretherketone (PEEK)

-^

Polyphenylene Sulfide

(PPS)

-^

Polythalamide (PPA)

-^

Polycarbonate

(PC)

-^

Polyvinyl

Chloride

(PVC)

-^

Acrylonitrile

butadiene

styrene

(ABS)

-^

Polyamide

(PA)

-^

Polyethylene

Terephthalate (PET)

-^

Polybutylene Terephthalate (PBT)

-^

Styrene

Acrylonitrile

(SAN)

-^

Polystyrene

(PS)

-^

High Impact polystyrene (HIPS)

-^

Polyoxymethylene (Acetal or

POM)

-^

Polypropylene

(PP)

-^

Polyethylene (HDPE/LDPE/LLDPE)

-^

High

Impact

polystyrene

(HIPS)

-^

Polymethylmethacrylate (PMMA

or

Acrylic)

-^

Polyethylene

(HDPE/LDPE/LLDPE)

Costs range from <$1.50/lb for Commodity to >$4/lb for Hi-Temp/Hi-Performance

Plastic Materials Selection

g^

y^

p

Data courtesy of RTP Company

Chemical

Structure

Influence

^

Acrylonitrile

butadiene

styrene

(ABS)

Amorphous

Pros

Cons

Good stiffness

Low maximum continuoususe temperature

E

ll^

t T

h^

use temperature

Excellent ToughnessClass A surface

Not resistant to solvents,hydrocarbons and fuels

PlatabilityResistant to alkalis and acids

Poor weatherability

•^

Specific

properties

dependent

on

amount

of

each

phase

^

Typical applications

^

Typical

applications

•^

Climate

control

and

radio

bezels

in

automotive

•^

Housings

in

consumer

electronics

and

appliances

Plastic Materials Selection

Chemical

Structure

Influence

^

Acetal (POM)

• Semi

‐crystalline

Pros

Cons

Good mechanical strength

Not resistant to acids

Excellent fatigue resistance

High specific gravity

g^

g^

p^

g^

y

Abrasion resistance

Anisotropic shrinkage

Low coefficient of friction

Processing difficulties

Low creep^ •

Specific

properties

dependent

on

homopolymer versus

copolymer

Low

creep Resistant to fuels and solvents

^

Typical

applications

•^

Fuel

system

components

in

automotive

•^

Gears

in

appliance

and

machinery

industries

Plastic Materials Selection

Chemical

Structure

Influence

^

Nylon

PA66)

Semi

‐crystalline

y^

,^

(^

)^

y

Pros

Cons

Excellent toughness

High water absorption

Heat resistance

Poor resistance to strongacids and bases

Abrasion resistanceResistant to fuels, solvents,

•^

Specific

properties

dependent

on

absorbed

water

content

^

T pical applications

,^

,

and hydrocarbons

^

Typical

applications

•^

Engine

and

cooling

system

components

in

automotive

•^

Cams

and

gears

in

appliance

and

machinery

industries

Plastic Materials Selection

Additives

^

Plasticizers

D

th

l^

t^

iti

t^

t^

(T )

ft

d^

dd

•^

Decreases

th

e^

glass

transition

temperature

(T

g),

softens

and

adds

flexibility

to

the

product

Flame

retardants

•^

Can

increase

resistance

to

ignition,

reduce

rate

of

burning,

flame

spread,

and

smoke

emission

• Halogenated

vs.

nonhalogenated

Property

Polypropylene HomopolymerUnfilled

V

V

Tensile Strength (

MPa

)^

32

23

30

Tensile

Strength (MPa)

32

23

30

Tensile Modulus (MPa)

1,

1,

1,

Impact Strength (J/m)

53

43

37

Plastic Materials Selection

Data courtesy of RTP Company

Additives

StabilizersStabilizers^ • UV,

oxidation,

hydrolysis,

etc…

Antistatic

agents

g

Blowing

agents

ColorantsColorants^ • Organic

vs.

inorganic

FillersFillers^ • Reinforcing,

non

‐reinforcing,

specialty

Plastic Materials Selection