Polymers in Automobiles Candace “Mustang” DeMartiHenry “Firebird” AntonovichKevin “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
Instrument Panels (IP) • Polycarbonate/ABS resins • Introduction of airbags in IP design • Injection Molding vs. Blow Molding
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: 1. Cost 2. Flexural Modulus 3. Coefficient of Thermal Expansion 4. Chemical Resistance 5. Impact Resistance 6. Heat Deflection Temperature (HDT)
Better color match • Incorporate in existing facilities • Assembly line temperatures exceed 200oCAlloys: • 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 “On-line” vs. “Off-line” painting
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
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, grille- opening 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 • Radial Ply-belts ofrubber coated cord • Innerliner • Reinforcing Fillers-carbon black • Chemicals-antidegradants, curitives
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.