Polymers in Automobiles
Candace “Mustang” DeMarti
Henry “Firebird” Antonovich
Kevin “Camaro” Reinhart
Overview
• Plastics vs. Metals
• Polymer Applications in Automobiles
- Instrument Panels
- Engine
- Windows
- Tires
- Body Panels
Why use plastics?
• Oil Embargo (1970’s) and Japanese
Competition
• Compete with other materials based on:
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Weight savings
Design flexibility
Parts consolidation
Ease of fabrication
Show & Tell
Car Part
Polymer
Trim Panels (3)
Polypropylene (PP)
Impact Absorber
Thermoplastic Olefin (TPO)
Radio Housing
ABS/Polycarbonate(PC)
Door Outer Panel
ABS/Polycarbonate(PC)
Handle
Polypropylene (PP)
Fog Light Cover
Thermoplastic Elastomeric
Olefin (TEO)
Elastomers
Tire
Application
Material
Processing Method
Load-Bearing
Glass-fiber reinforced
Pressing of resin
- bumper beams
polyester resins
compounds
Moldings/covers Polyurathane
Injection Molding
- front apron
Polypropylene
- spoiler
Polyethlene
- wheel-well liners
Acrylonitrile-butadiene- radiator grill
styrene (ABS)
- hood
Polycarbonate
- fenders
- trunk
Protective
Moldings
Energy
Absorbing Foam
Polyvinyl chloride
Ethylene-Propylene
Terpolymers
Polyurethane
Injection Molding/
Extrusion
Liquid Reaction
Foaming
Instrument Panels (IP)
• Polycarbonate/ABS resins
• Introduction of airbags in IP design
• Injection Molding vs. Blow Molding
Instrument Panels (IP)
Engine
• ULTEM polyetherimide (PEI) resin to replace
aluminum under the hood for 1st time
• High-performance
amorphous resin from GE
• Complete air management
modules can be made of
thermoplastic
Throttle Body
Body Panels
• Plastic Body Panels Chevy Corvette since
1953
Sheet Steel - still most commonly used for vehicle
body structure
Aluminum - weighs less but costs more
Plastics - increasingly used for metals parts
replacement
Choosing a material:
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Cost
Flexural Modulus
Coefficient of Thermal Expansion
Chemical Resistance
Impact Resistance
Heat Deflection Temperature (HDT)
“On-line” vs. “Off-line” painting
• Better color match
• Incorporate in existing
facilities
• Assembly line
temperatures exceed
200oC
Alloys:
Polyphenylene ether/polyamide
ABS/Polyesters
ABS/Polycarbonates
• Larger choice in
materials
• Additional steps take
time
• More plastics will
enter the market as
assembly lines are
redesigned
Sheet Molding Compound
(SMC)
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Highly cross-linked and highly filled
Polymer component is polyester
Suitable of compression molding
Molded product combined high modulus
with high strength
• Body panels (hoods and deck lids)
• More expensive than metal, but lower
tooling cost
Applications of SMC
• Bottom line benefits
– Tooling for SMC hood was 23% of steel
– Weight savings of 18%
• Growth of applications
- Body panels on GM’s Lumina, TransPort, and
Silhouette
- Structural components - valve covers, grilleopening reinforcements, fascia supports, etc.
• 250 million lbs. of SMC was used in 1997
Applications of SMC
• Composite front fenders and hood design
for 1995 Lincoln Continental
• Result of need for lighter-weight and more
cost efficiency integrated system
• SMC fenders and hood
• Bottom line benefits:
– SMC fender tooling was 40% of projected
tooling for steel fenders
– Comparative weight saving was 33%
Solitary Bumper Beam
• For 1997 Saturn coupe
• Injection molded from GE Plastics’
Xenoy 1102
• Single part that replaces functions of
17 parts on previous system
• To absorb impact, specially designed
molded-in towers crush upon impact
Windshields
• Toughened Safety Glass (TSG)
- tempered glass
• Laminated Safety Glass (LSG)
- two panes of glass bonded together
using polyvinylbutyral
Tire Components
• Tread
• Sidewall
• Bead-high tensile brass-plated steel
coated with rubber
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Radial Ply-belts of rubber coated cord
Innerliner
Reinforcing Fillers-carbon black
Chemicals-antidegradants, curitives
Desirable Properties of Tire
Components
Maximum
Minimum
Tread
Traction
Wear, Cut Growth,
Roll Resistance
Sidewall
Adhesion,
Oxidative Stability,
Cleanability
Weather Cracking,
Flex Cracking, Heat
Buildup, Scuffing
Wire Coat
Wire Adhesion
Heat Buildup
Ply Coat
Cord Adhesion
Heat Buildup
Innerliner
Ply Adhesion,
Oxidative Stability
Air Permeability,
Flex Cracking,
Heat Buildup
Elastomers in Tires
• Natural Rubber (NR)
• Polyisoprene Rubber (IR)
• Styrene Butadiene Rubber (SBR)
- 1.89 billion lbs/yr (1993)
• Polybutadiene Rubber (BR)
- 1.03 billion lbs/yr (1993)
Natural Rubber (NR)
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99.99% cis Polyisoprene
Good low temperature flexibility.
Low Tg (-65 C). Low heat buildup.
200,000 to 400,000 MW. Easy Processing.
Has high tensile and tear properties. Stress
crystallizes.
• Excellent dynamic fatigue
• Poor resistance to oxygen, ozone,
hydrocarbon solvents and heat.
Polyisoprene Rubber (IR)
• Same cis structure as NR, but also contains
low levels of 3,4 and trans 1,4 polyisoprene.
• Above structures prevent stress
crystallization and thus has lower tensile
and tear properties.
• 300,000 to 500,000 MW.
• Other properties similar to NR .
Polybutadiene Rubber (BR)
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Good low temperature flexibility.
High abrasion resistance.
Low heat buildup.
Low tensile strength. Generally
blended with SBR or NR.
• Improves aging resistance of NR.
Styrene Butadiene Rubber
(SBR)
• Dynamic properties determined by styrene,
1,4 and 1,2 butadiene levels.
• Improved strength, abrasion resistance, and
blend compatibility over BR alone.
• Addition of styrene results in lower cost and
contributes to the good wearing and bonding
characteristics.
Elastomers Used in Tire
Components
Tread
NR
BR
SBR
Sidewall
NR
BR
SBR
Wire Coat Ply Coat
NR
BR
IR
NR
BR
SBR
IR
Innerliner
NR
SBR