Rubber Composition for Tire Sidewalls
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Solution Overview
Problem
Conventional rubber compositions for tire sidewalls face challenges in achieving a balance between cohesion, rigidity, hysteresis, and ozone resistance, particularly when the molar rate of ethylene in ethylene and 1,3-diene copolymers exceeds 50%, leading to a decline in cohesive properties.
Innovation Solution
A rubber composition comprising natural rubber, a highly saturated diene elastomer with ethylene units exceeding 50% by mole, carbon black at 20-40 phr, and a crosslinking system, with the carbon black volume fraction between 8-15%, and a crosslinking system based on sulfur or sulfur donors, peroxide, and bismaleimides, to enhance properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the molar rate of ethylene in the copolymer is increased to improve ozone resistance and rigidity, then ozone resistance and rigidity are improved, but cohesive properties deteriorate
Solution Approach 1:
The patent optimizes the ethylene content parameter within a specific range (50-80 mol%) rather than using high ethylene content copolymers (>80 mol%). This parameter optimization maintains adequate cohesive properties while achieving improved ozone resistance and rigidity. The patent also optimizes the copolymer content (20-50 phr) and carbon black content (20-40 phr) to balance cohesive properties with other performance requirements.
Solution Approach 2:
The patent creates a composite rubber composition by combining natural rubber (50-80 phr) with ethylene-1,3-diene copolymer (20-50 phr) and carbon black (20-40 phr). This composite approach allows the natural rubber to provide cohesive properties while the copolymer provides ozone resistance and rigidity, and carbon black enhances reinforcement. The synergistic combination resolves the contradiction between cohesive properties and ozone resistance/rigidity.
2Stress or pressure
If the molar rate of ethylene in the copolymer is increased to improve rigidity, then rigidity is improved, but cohesive properties deteriorate
Solution Approach 1:
The patent specifies ethylene content in the copolymer within the range of 50-80 mol%, which provides sufficient rigidity for tire sidewalls while maintaining adequate cohesive properties. This optimized parameter range avoids the cohesive property deterioration that occurs with higher ethylene content copolymers (>80 mol%).
Solution Approach 2:
The composite formulation combines natural rubber (providing cohesion) with ethylene-1,3-diene copolymer (providing rigidity) in specific proportions. The natural rubber component compensates for the reduced cohesion in high-rigidity copolymers, while the copolymer provides the necessary rigidity for sidewall applications.
3Reliability
If the rate of copolymer in the rubber composition is increased to improve ozone resistance, then ozone resistance is improved, but cohesive properties deteriorate
Solution Approach 1:
The patent optimizes the copolymer content within the range of 20-50 phr (parts per hundred rubber). This optimized concentration provides sufficient ozone resistance while maintaining adequate cohesive properties. Higher copolymer concentrations would improve ozone resistance further but would deteriorate cohesive properties.
Solution Approach 2:
The patent creates a balanced composite where natural rubber (50-80 phr) provides cohesive properties and the copolymer (20-50 phr) provides ozone resistance. This compositional balance ensures that neither property deteriorates, as each component compensates for the other's limitations.
4Strength
If the level of carbon black is increased to improve reinforcement and cohesion, then cohesive properties and reinforcement are improved, but hysteresis increases
Solution Approach 1:
The patent optimizes carbon black content within the range of 20-40 phr, which provides adequate reinforcement and cohesive properties while limiting excessive hysteresis. This optimized concentration balances the competing requirements of strength and energy loss.
Solution Approach 2:
The composite formulation uses carbon black (20-40 phr) as a reinforcing filler that enhances both cohesion and strength. The natural rubber and copolymer matrix provides a balance between reinforcement and hysteresis control, as the elastomeric components reduce the energy loss associated with high carbon black loading.
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 composition achieves improved performance in rigidity, hysteresis, cohesion, and ozone resistance, making it suitable for tire sidewalls with enhanced durability and resistance to deformation cycles and ozone exposure.
Implementation Method 1
the level of carbon black in the rubber composition varying from 20 phr to 40 phr, the volume fraction of the carbon black in the rubber composition varying from 8% to 15%
Implementation Method 2
a system crosslinking based on sulfur or sulfur donors, peroxide, and bismaleimides
Implementation Method 3
the rubber composition constituting a sidewall of a tire must be both sufficiently flexible and not very hysteretic
Implementation Method 4
a rubber composition which constitutes a sidewall must have good ozone resistance properties
Data Source
AI summary
The present invention concerns a rubber composition made from at least natural rubber, an ethylene copolymer and a 1,3-diene, a carbon black and a cross-linking system, wherein the content of carbon black varies from 20 phr to 40 phr, the volume fraction of the carbon black varies from 8% to 15%, the content of copolymer varies from 20 phr to less than 50 phr, the natural rubber content is greater than 50 phr, the copolymer contains more than 50 mol% ethylene. Such a composition provides an improved compromise between the properties of cohesion, rigidity, hysteresis and ozone resistance. Such a composition is preferably used in a sidewall for a tyre.