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: – – – – 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: 1. 2. 3. 4. 5. 6. 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) • • • • 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 • • • • 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) • • • • • 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 NR BR SBR Sidewall NR BR SBR Wire Coat Ply Coat NR BR IR NR BR SBR IR Innerliner NR SBR