Styrene/Butadiene Elastomer Blend for Tire Traction and Heat Control
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Solution Overview
Problem
Ultra high performance pneumatic tires face challenges in maintaining dry traction while ensuring wet traction and reducing internal heat generation, which can lead to tire durability issues due to high glass transition temperature elastomers causing increased hysteresis and heat generation.
Innovation Solution
A rubber composition combining solution and emulsion prepared styrene/butadiene elastomers with selectively distributed softening points, pre-hydrophobated precipitated silica, and small particle sized carbon black to balance tread rubber stiffness and hysteresis across a wide temperature range, promoting both dry and wet traction without excessive heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high Tg elastomers are used to promote dry traction, then dry traction is improved, but internal heat generation increases due to increased hysteresis
Solution Approach 1:
The patent uses a combination of three different styrene/butadiene elastomers with specifically controlled glass transition temperatures (Tg) and vinyl contents. By selecting elastomers with Tg values of -50°C to -30°C, -30°C to -20°C, and -20°C to -10°C respectively, the composition achieves optimal dry traction while controlling hysteresis and internal heat generation through parameter optimization rather than using a single high Tg elastomer.
Solution Approach 2:
The patent creates a composite rubber composition by combining three different styrene/butadiene elastomers with distinct Tg ranges and vinyl contents, along with carbon black and silica fillers. This composite approach allows the composition to exhibit synergistic effects where the combination provides better dry traction and heat resistance than any single elastomer alone, effectively resolving the contradiction between traction and heat generation.
2Strength
If high Tg elastomers are used to promote dry traction, then dry traction is improved, but tread cracking occurs due to reduced flexibility
Solution Approach 1:
The patent distributes the Tg values across three elastomers ranging from -50°C to -10°C, ensuring that at least some elastomer components remain flexible at operating temperatures. This parameter distribution prevents the entire tread compound from becoming too rigid, thereby maintaining cracking resistance while achieving dry traction through the combined effect of all elastomers.
Solution Approach 2:
Different elastomers with specific Tg ranges are assigned to provide different local functions: lower Tg elastomers maintain flexibility and prevent cracking, while higher Tg elastomers contribute to dry traction. This local quality differentiation within the composite composition allows simultaneous achievement of both dry traction and cracking resistance.
3Strength
If resins with higher softening points are used to promote traction at high temperatures, then high-temperature traction is improved, but hysteresis increases leading to more internal heat generation
Solution Approach 1:
The patent carefully controls the softening points of the resins used in the composition. By selecting resins with appropriate softening points that are not excessively high, the composition maintains traction capability at elevated temperatures while avoiding excessive softening that would increase hysteresis and internal heat generation. This parameter optimization resolves the contradiction between high-temperature traction and heat generation.
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 enhances traction performance and handling capabilities over a broad temperature range while reducing tread cracking and internal heat generation, meeting target properties for dry and wet traction and hysteresis reduction.
Implementation Method 1
A significant challenge for such ultra high performance tires is to provide a rubber composition to promote dry traction for the tread while maintaining wet traction through use of high Tg elastomers with attenuation of normally increasing internal heat generation of the tread rubber composition by limiting increased hysteresis of the rubber composition
Implementation Method 2
the primary traction requirement is directed to dry traction while still maintaining wet traction. This challenge often presents other issues such as having tread rubber compositions with greater internal heat generation during tire service with associated higher tire running temperature which may result in reduced tire durability. Such increase in internal heat generation is, in general, a promotion of increased hysteresis of the tread rubber composition by the inclusion of the high Tg (high glass transition temperature) elastomers
Data Source
AI summary
A rubber composition is disclosed comprising, based on parts by weight per 100 parts by weight rubber (phr), (A) conjugated diene-based elastomers comprising: (1) from 20 to 70 phr of a solution polymerization prepared styrene/butadiene elastomer (S-SBR-A) having a styrene content in a range of from 35 to 45 percent and a Tg in a range of from -30°C to -50°C, (2) from 20 to 60 phr of a solution polymerization prepared styrene/butadiene elastomer (S-SBR-B) having a styrene content in a range of from 35 to 45 percent and a Tg in a range of from -3°C to -23°C, and (3) from 5 to 30 phr of an aqueous emulsion polymerization prepared styrene/butadiene elastomer (E-SBR) having a styrene content in a range of from 35 to 45 percent and a Tg in a range of from -30°C to -50°C; wherein said Tg's of said S-SBR-A, S-SBR-B and E-SBR are spaced apart from each other by at least 4°C; and (B) from 8 to 30 phr of at least three, preferably from three to five, different resins selected from the group polyester phthalate resin, styrene/alphamethyl styrene resin, gum rosin, coumarone indene resin and alkylphenol acetylene resin. The rubber composition may be used in a tread of a pneumatic tire.