1. CE 435 -- Intoduction to Polymers 1
Firestone Tires
Parag Patel
Joshua Pun
Cory Robinson
2. CE 435 -- Intoduction to Polymers 2
Outline
Introduction
Tire Production
Overview of Tread Separation Problem
Legal Matters
Conclusion/Questions
3. CE 435 -- Intoduction to Polymers 3
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
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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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Chemistry of Tires - Introduction
Overview of Vulcanization Process
Description of Brass-on-Wire
Adhesion
2nd Major Issue in Faulty Firestone
Tires
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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.
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Properties
Source: Mark, James E. Science and Technology of Rubber. Academic: San Diego, CA, 1994
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Vulcanization (con’t)
Heat with and without accelerators
– Without: 5 hrs @ 140 oC / 8 phr sulfur
– 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)
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Mechanisms
Source: Mark, James E. Science and Technology of Rubber. Academic: San Diego, CA, 1994
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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
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Brass-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 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 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 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)
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/A
Firestone liability in poor quality
control & tread design
Ford maintains 26 psi sufficient, but
has changed target to 30-35 psi.
Questions