Firestone Tires Parag Patel Joshua Pun Cory Robinson CE 435 -- Intoduction to Polymers 1 Outline Introduction Tire Production Overview of Tread Separation Problem Legal Matters Conclusion/Questions CE 435 -- Intoduction to Polymers
2 Introduction Charles Goodyear 1800 1860 1821: Went into hardware business 1833: Started making rubber goods 1834: Failure in first rubber venture 1837: Eliminated some of the rubber defects 1838: Bought patent from partner 1844: Discovered Vulcanization CE 435 -- Intoduction to Polymers 3
Tire Production Statistics: 1999 Co./Headquarters Bridgestone Corp. Tokyo, J apan Michelin et Cie. Clermont-Ferrand, France Goodyear Tire & Rubber Co. Akron, Ohio/USA Continental A.G. Hanover, Germany Sumitomo Rubber Industries Ltd. Kobe, J apan Pirelli S.p.A. Milan, Italy Yokohama Rubber Co. Ltd. Tokyo, J apan
1998 Tire Sales % of Total Tire Sales % of Total (Millions $) Corp. Sales (Millions $) Corp. Sales
13,500.00 74% 12,634.80 74% 13,500.00 92% 12,916.30 93% 11,515.60
85% 11,311.00 85% 4,900.00 50% 4,334.00 58% 3,413.80 76%
3,750.00 75% 2,725.20 40% 3005.8 49% 2,408.20 70% 2193.5
70% Source: http://www.rubbernews.com/subscriber/charts/global.html CE 435 -- Intoduction to Polymers 4 Raw Materials Fabric (steel, polyester, nylon, etc.) Rubber (synthetic, natural, or blends) Reinforcing Chemicals (silica, resins, etc.) Anti-Degradant (Ozonants, paraffin waxes) Adhesion Promoters (brass, cobalt salts) Curatives (cure accelerators, activators, sulfur) Processing Oils (Oils, Tackifiers, Softeners)
CE 435 -- Intoduction to Polymers 5 Processing & Production Mix Process Oils, Rubber, Reinforcers, Accelerators, & Anti-Degradants Coatings Fabric Steel Belt Bead CE 435 -- Intoduction to Polymers 6
CE 435 -- Intoduction to Polymers 7 Processing & Production (cont) Components assemble taken to tire machine for Inner liner Ply Fabric (two layers) possible cause of problem Apexes Chafer Strips Steel Belts Curing
Inspection CE 435 -- Intoduction to Polymers 8 CE 435 -- Intoduction to Polymers 9 Chemistry of Tires - Introduction Overview of Vulcanization Process Description of Brass-on-Wire Adhesion 2nd Major Issue in Faulty Firestone Tires
CE 435 -- Intoduction to Polymers 10 Vulcanization Process by which rubber is chemically crosslinked (e.g. disulfides) Makes material stronger, elastic, resistant to solvents, and moderate heat/cold. Rubber is heated in the presence of sulfur and accelerator. CE 435 -- Intoduction to Polymers 11
Properties Source: Source Mark, James E. Science and Technology of Rubber. Academic: San Diego, CA, 1994 CE 435 -- Intoduction to Polymers 12 Vulcanization (cont) Heat with and without accelerators Without: Without 5 hrs @ 140 oC / 8 phr sulfur With: With 1-3 min @ 140 oC / 0.5 phr sulfur
Main Considerations: Size and type of object (thick walled -> longer curing time) Compound vulcanizabliity and flowability Type of vulcanization (mould vs. boiler) Maximum vulcanization temperature of material or system Removal of article from mould (higher temp, more difficult) CE 435 -- Intoduction to Polymers
13 Mechanisms Source: Source Mark, James E. Science and Technology of Rubber. Academic: San Diego, CA, 1994 CE 435 -- Intoduction to Polymers 14 Brass-on-Wire Adhesion Process by which brass (CuZn) deposited on steel belts Important for proper metal/rubber adhesion
Care must be taken to prevent oxidation of both brass and steel CE 435 -- Intoduction to Polymers 15 Brass-on-Wire Adhesion Formation of Copper Sulfide Layer Rubber infiltration into porous CuS layer Prevent ZnS/FeS layers (not porous) CE 435 -- Intoduction to Polymers 16
Faulty Tires Brass on Wire coatings must be strictly monitored. Coated/Uncoated wire should be kept in environmentally controlled conditions. Free from particulate matter. Employee accusations of improper handling Poor quality control Used oxidized/improperly handled wire CE 435 -- Intoduction to Polymers 17 Cause of Problem The
Ford Motor Company -size of the Ford Explorer -recommended tire pressure too low Drivers of the Vehicles -improper maintenance of tires -wear and tear CE 435 -- Intoduction to Polymers 18 Legal Matters Both Firestone and Ford are in an ongoing battle with the public Bridgestone/Firestone Position
-taken the responsibility for faulty design -initiated world wide recall -offered free replacements -still believe blame should not wholly be on them CE 435 -- Intoduction to Polymers 19 Legal Matters (cont) Ford Motors Corporations Position -stands by their design of Ford Explorers -changed recommended tire pressure Plaintiffs
Position -continue to file lawsuits -boycott product manufactured by Ford and Firestone CE 435 -- Intoduction to Polymers 20 Conclusions & Q/A Firestone liability in poor quality control & tread design Ford maintains 26 psi sufficient, but has changed target to 30-35 psi. Questions
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