Polymers in Automobiles

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Polymers in Automobiles
Candace Mustang DeMartiHenry Firebird
AntonovichKevin Camaro Reinhart
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Overview

• Plastics vs. Metals
• Polymer Applications in Automobiles- Instrument
  Panels- Engine- Windows- Tires- Body Panels

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Why use plastics?

• Oil Embargo (1970s) and Japanese Competition
• Compete with other materials based on
• Weight savings
• Design flexibility
• Parts consolidation
• Ease of fabrication

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Instrument Panels (IP)

• Polycarbonate/ABS resins
• Introduction of airbags in IP design
• Injection Molding vs. Blow Molding

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Instrument Panels (IP)
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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
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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
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Choosing a material

• 1. Cost
• 2. Flexural Modulus
• 3. Coefficient of Thermal Expansion
• 4. Chemical Resistance
• 5. Impact Resistance
• 6. Heat Deflection Temperature (HDT)

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• 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

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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

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Applications of SMC

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

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

• 250 million lbs. of SMC was used in 1997

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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

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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

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Windshields

• Toughened Safety Glass (TSG)- tempered glass
• Laminated Safety Glass (LSG)- two panes of glass
  bonded together using polyvinylbutyral

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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

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Desirable Properties of Tire Components
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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)

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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.

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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 .

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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.

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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.

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Elastomers Used in Tire Components