Low-Sulfur Elastomeric Mixtures for Tire Endurance
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Solution Overview
Problem
Heavy-duty tires face premature aging and reduced endurance due to shear stresses and increased operating temperatures, leading to crack formation and potential air loss from perforations, which can result in undetected slow air leaks and premature tire degradation.
Innovation Solution
A tire design with a radial carcass reinforcement featuring elastomeric mixtures with a relative density of sulfur bridges less than 5%, used in specific layers to reduce crack propagation and enhance resistance to aging, combined with a polymeric mixture layer extending to the axial ends of the tread and carcass reinforcement, minimizing the impact of object penetrations and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional elastomeric mixtures with high sulfur content are used in the carcass reinforcement and protective layers, then the tire has good initial strength and resistance to deformation, but the tire exhibits premature aging, crack formation, and reduced endurance due to shear stresses and high operating temperatures
Solution Approach 1:
The patent changes the chemical composition parameter of the elastomeric mixtures by reducing sulfur content to less than 5% in the carcass reinforcement and protective layers, replacing traditional high-sulfur formulations. This parameter change reduces susceptibility to oxidation and thermal degradation, thereby improving endurance while maintaining adequate initial strength through alternative vulcanization systems.
Solution Approach 2:
The patent uses composite elastomeric formulations combining multiple rubber types (natural rubber, polybutadiene, polyisoprene) with specific sulfur content limitations. This composite approach creates a material that balances initial mechanical properties with improved aging resistance, solving the contradiction between strength and durability.
2Productivity
If the tire operates at high speeds for long journeys, then the tire covers more kilometers with less wear, but the endurance of the crown frame is penalized due to increased operating temperature and shear stresses causing crack propagation
Solution Approach 1:
The patent modifies the thermal and chemical parameters of the elastomeric mixtures by limiting sulfur content and specifying maximum operating temperatures (below 80°C in protective layers). These parameter changes reduce thermal degradation and oxidation rates, allowing the tire to maintain reliability under high-productivity operating conditions.
Solution Approach 2:
The patent applies protective layers with specific elastomeric compositions before cracks can form and propagate. These pre-applied low-sulfur elastomeric layers act as a cushion against thermal and mechanical stresses, preventing crack initiation and propagation before they compromise the crown frame integrity during high-mileage operation.
3Quantity of substance
If objects penetrate the tread to the internal cavity, then air loss occurs, but the presence of oxygen accelerates oxidation and crack propagation in the elastomeric mixtures
Solution Approach 1:
The patent changes the chemical composition of elastomeric mixtures in the carcass reinforcement and protective layers by reducing sulfur content below 5%. This compositional change reduces the material's susceptibility to oxidation when exposed to oxygen from punctures, slowing crack propagation even when air loss occurs.
Solution Approach 2:
The patent acknowledges that punctures causing air loss also remove oxygen from the tire interior. By using low-sulfur elastomeric formulations, the patent converts the harmful effect of oxygen exposure into a less severe condition, where the reduced sulfur content means less oxidation damage even when oxygen is present from puncture events.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The tire exhibits improved endurance and resistance to crack propagation, allowing for extended use and potential retreading even after punctures, with a 30% increase in kilometers traveled before retreading becomes prohibited by cracking, and reduced hysteresis values for improved rolling resistance.
Implementation Method 1
the presence of oxygen leads to oxidizing processes, rubber compositions and/or metallic or textile reinforcements and/or interfaces between these rubber compositions and these reinforcements
Implementation Method 2
said elastomeric mixtures forming the calendering layer, radially outermost at the top of the tire, of said at least one carcass reinforcement layer and said elastomeric mixtures forming said at least one layer P
Implementation Method 3
There are in fact constraints at the level of the top reinforcement and more particularly shear stresses between the top layers
Implementation Method 4
the triangulation sheet having the essential role of taking up the transverse compression forces
Implementation Method 5
The triangulation sheet forms with at least said working sheet a triangulated reinforcement, which presents, under the different stresses it undergoes, few deformations
Data Source
Figure 1
AI summary
The invention concerns a tyre having a radial carcass reinforcement (2), consisting of at least one layer, comprising a crown reinforcement (3) radially hooded by a tread layer (4), said tyre comprising a layer P of polymeric mixtures in contact with at least one working crown layer (31, 32) and in contact with the carcass reinforcement. According to the invention, at least the elastomeric mixtures forming the calendering layer, radially the most external to the crown of the tyre, of the carcass reinforcement layer, have a relative density of sulfur bridges of less than 5% and the elastomeric mixtures forming the layer P have a relative density of sulfur bridges of less than 5%, said elastomeric mixtures being compositions made from at least one diene elastomer chosen from the group of diene elastomers consisting of polybutadienes (abbreviated as "BR"), synthetic polyisoprenes (IR), natural rubber (NR), isoprene copolymers, butadiene copolymers with the exception of nitrile butadiene copolymers (NBR), excluding diene elastomers carrying carboxyl functions, and the mixtures of said diene elastomers.