Epoxidized Polyisoprene Rubber Composition for Tire Rigidity and Hysteresis
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Solution Overview
Problem
Rubber compositions for tires face a challenge in achieving a balance between cured rigidity and hysteresis, as increasing filler rates or using styrene-butadiene copolymers to enhance rigidity often leads to increased hysteresis, resulting in higher internal tire temperatures and reduced durability.
Innovation Solution
A rubber composition comprising 0 to less than 20 phr of butyl rubber, more than 50 to 100 phr of a polyisoprene matrix with epoxidized polyisoprene, carbon black with a mass greater than 50% of the total carbon black and silica, and a crosslinking system, which improves the compromise between stiffness and hysteresis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the filler rate is increased to increase cured rigidity, then cured rigidity is improved, but hysteresis increases
Solution Approach 1:
The patent changes the chemical composition parameters of the rubber matrix by incorporating epoxidized natural rubber (ENR) with specific epoxidation levels (5% to less than 50%, preferably 10% to 30%). This chemical modification allows achieving the desired cured rigidity without relying solely on increased filler content, thereby avoiding the hysteresis penalty associated with high filler rates.
Solution Approach 2:
The patent creates a composite rubber system combining epoxidized natural rubber with conventional natural rubber and specific filler packages (carbon black and silica). This composite approach leverages the polar groups from epoxidation to enhance filler-rubber interaction, achieving improved rigidity through optimized material composition rather than simply increasing filler quantity.
2Strength
If copolymers of styrene and butadiene with high styrene content are introduced to increase cured rigidity, then cured rigidity is improved, but hysteresis increases
Solution Approach 1:
The patent modifies the rubber matrix composition by introducing epoxidized natural rubber with controlled epoxidation levels (5% to less than 50% molar epoxidation). This chemical parameter change provides a alternative mechanism for achieving cured rigidity that does not rely on high styrene content copolymers, thereby avoiding the hysteresis increase associated with such copolymers.
3Reliability
If hysteresis is reduced to improve tire endurance, then tire durability is improved, but cured rigidity may be compromised
Solution Approach 1:
The patent utilizes epoxidized natural rubber with specific epoxidation levels (5% to less than 50%) to modify the rubber matrix properties. The polar epoxy groups enhance filler-rubber interaction and improve the rubber's inherent stiffness, allowing reduced hysteresis without compromising cured rigidity through the chemical modification of the polymer structure itself.
Solution Approach 2:
The patent employs a composite system combining epoxidized natural rubber, conventional natural rubber, and optimized filler packages. This composite approach achieves low hysteresis and high cured rigidity simultaneously by leveraging synergistic interactions between the epoxidized polymer matrix and the filler particles, creating a material that dissipates less energy while maintaining structural strength.
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 increased cured rigidity without increasing hysteresis, leading to improved tire endurance and performance by maintaining a balance between wear resistance and durability.
Implementation Method 1
a polyisoprene matrix, the polyisoprene matrix containing an epoxidized polyisoprene
Implementation Method 2
a crosslinking system
Data Source
AI summary
The present invention relates to a rubber composition improving the trade-off between the baking rigidity and the hysteresis of the composition. Said composition contains: 0 to less than 20 phr of butyl rubber; more than 50 to 100 phr of a polyisoprene matrix, the polyisoprene matrix containing an epoxidized polyisoprene having an epoxidation molar ratio of 5% to less than 0%; a carbon black and a silica, the carbon black weight being greater than 50% of the total weight of carbon black and silica; 0 to less than 2 phr of a coupling agent; and a crosslinking system. The epoxidized polyisoprene is a natural epoxidized rubber, a synthetic epoxidized polyisoprene having a cis-1,4 bond molar ratio of at least 90% before epoxidation, or the mixture thereof, with the proviso that, if the epoxidized polyisoprene is an epoxidized polyisoprene having an epoxidation molar ratio of 5% to 25%, the rubber composition contains more than 50 phr of epoxidized polyisoprene.