CE 435 -- Intoduction to Polymers 1

Firestone TiresFirestone Tires

Parag PatelJoshua Pun

Cory Robinson

CE 435 -- Intoduction to Polymers 2

OutlineOutline

IntroductionTire ProductionOverview of Tread Separation ProblemLegal MattersConclusion/Questions

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IntroductionIntroduction

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

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Tire ProductionTire Production Statistics:

Source: http://www.rubbernews.com/subscriber/charts/global.html

Tire Sales % of Total Tire Sales % of Total(Millions $) Corp. Sales (Millions $) Corp. Sales

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

2,408.20 70% 2193.5 70%

2,725.20 40% 3005.8 49%

3,413.80 76% 3,750.00 75%

4,900.00 50% 4,334.00 58%

11,515.60 85% 11,311.00 85%

13,500.00 92% 12,916.30 93%

1999 1998

Co./Headquarters

13,500.00 74% 12,634.80 74%

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Raw Materials 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)

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Processing & ProductionProcessing & Production Mix Process Oils, Rubber, Reinforcers,

Accelerators, & Anti-Degradants Coatings– Fabric– Steel Belt

Bead

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CE 435 -- Intoduction to Polymers 8

Processing & Production (con’t)Processing & Production (con’t) Components taken to tire machine for

assemble– Inner liner– Ply Fabric (two layers) – possible cause of

problem– Apexes– Chafer Strips– Steel Belts– Curing– Inspection

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CE 435 -- Intoduction to Polymers 10

Chemistry of Tires - IntroductionChemistry of Tires - Introduction

Overview of Vulcanization ProcessDescription of Brass-on-Wire

Adhesion2nd Major Issue in Faulty Firestone

Tires

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VulcanizationVulcanization

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.

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PropertiesProperties

SourceSource: Mark, James E. Science and Technology of Rubber. Academic: San Diego, CA, 1994

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Vulcanization (con’t)Vulcanization (con’t) Heat with and without accelerators

– WithoutWithout: 5 hrs @ 140 oC / 8 phr sulfur– WithWith: 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)

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MechanismsMechanisms

SourceSource: Mark, James E. Science and Technology of Rubber. Academic: San Diego, CA, 1994

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Brass-on-Wire AdhesionBrass-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

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Brass-on-Wire AdhesionBrass-on-Wire Adhesion

Formation of Copper Sulfide Layer Rubber infiltration into porous CuS layer Prevent ZnS/FeS layers (not porous)

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Faulty TiresFaulty 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

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Cause of ProblemCause 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

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Legal MattersLegal 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

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Legal Matters (con’t)Legal Matters (con’t)

Ford Motors Corporation’s Position-stands by their design of Ford Explorers-changed recommended tire pressure

Plaintiff’s Position-continue to file lawsuits-boycott product manufactured by Ford and Firestone

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Conclusions & Q/AConclusions & Q/A

Firestone liability in poor quality control & tread design

Ford maintains 26 psi sufficient, but has changed target to 30-35 psi.

Questions