Polymers in Automobiles

Candace “Mustang” DeMartiHenry “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:– Weight savings– Design flexibility– Parts consolidation– Ease of fabrication

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 ElastomericOlefin (TEO)

Tire Elastomers

Show & Tell

Application Material Processing MethodLoad-Bearing- bumper beams

Glass-fiber reinforced polyester resins

Pressing of resincompounds

Moldings/covers- front apron- spoiler- wheel-well liners- radiator grill- hood- fenders- trunk

PolyurathanePolypropylenePolyethleneAcrylonitrile-butadiene- styrene (ABS)Polycarbonate

Injection Molding

ProtectiveMoldings

Polyvinyl chlorideEthylene-PropyleneTerpolymers

Injection Molding/Extrusion

EnergyAbsorbing Foam

Polyurethane Liquid ReactionFoaming

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 structureAluminum - weighs less but costs morePlastics - increasingly used for metals parts

replacement

Choosing a material:

1. Cost2. Flexural Modulus3. Coefficient of Thermal Expansion4. Chemical Resistance5. Impact Resistance6. 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/PolyestersABS/Polycarbonates

• Larger choice in materials• Additional steps take time• More plastics will enter the market as assembly lines are redesigned

Sheet Molding Compound (SMC)

• 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

• Growth of applications- Body panels on GM’s Lumina, TransPort, and Silhouette- Structural components - valve covers, grille- opening reinforcements, fascia supports, etc.

• 250 million lbs. of SMC was used in 1997

Applications of SMC

• Bottom line benefits– Tooling for SMC hood was 23% of steel– Weight savings of 18%

• 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%

Applications of SMC

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

• 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, HeatBuildup, 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)

• 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)

• 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 Sidewall Wire Coat Ply Coat Innerliner

NRBRSBR

NRBRSBR

NRBRIR

NRBRSBRIR

NRSBR