Butyl Rubber Composition with Graphite and Carbon Black
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Solution Overview
Problem
Current rubber compositions for tire interiors face challenges in achieving low weight and hysteresis while maintaining impermeability and mechanical properties, as semi-reinforcing fillers like graphite, when used in large quantities, can deteriorate essential properties such as bending resistance and cold rigidity.
Innovation Solution
A rubber composition comprising butyl rubber, carbon black at a specific range (2-15 phr), graphite at a high content (≥60 phr), and a plasticizing oil at a limited content (≤30 phr), which improves mechanical properties like breaking stress and energy without compromising impermeability and cold rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large quantities of semi-reinforcing fillers (graphite) are added to improve impermeability, then air impermeability is improved, but mechanical properties (bending resistance and cold rigidity) deteriorate
Solution Approach 1:
The patent applies composite materials by combining butyl rubber with a specific mixture of reinforcing fillers (carbon black at 2-15 phr) and semi-reinforcing fillers (graphite at ≥60 phr). This composite approach allows the composition to achieve both improved impermeability from the graphite and maintained mechanical properties from the carbon black, resolving the contradiction between these two properties.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the quantities of different fillers - limiting carbon black to 2-15 phr while requiring graphite to be at least 60 phr, with plasticizing oil limited to ≤30 phr. This specific parameter optimization allows the composition to achieve the desired balance between impermeability and mechanical properties.
2Strength
If plasticizing oils are added to improve mechanical properties, then bending resistance and cold rigidity are improved, but impermeability is severely reduced
Solution Approach 1:
The patent applies parameter changes by strictly limiting the plasticizing oil content to 30 phr or less, while compensating for mechanical property requirements through the optimized filler composition (carbon black and graphite in specific ratios). This parameter control prevents the impermeability deterioration that occurs with higher oil contents.
Solution Approach 2:
The patent uses carbon black and graphite as filler materials that can partially substitute for the functional role of plasticizing oils in providing mechanical strength, while maintaining the impermeability that would otherwise be compromised by oil addition.
3Reliability
If the thickness of butyl rubber is increased to improve impermeability, then air impermeability is improved, but weight increases
Solution Approach 1:
The patent applies composite materials by incorporating high levels of graphite (≥60 phr) into the butyl rubber composition. The graphite particles create a tortuous path for gas permeation, improving impermeability without requiring increased thickness, thereby avoiding the associated weight increase.
Solution Approach 2:
The patent applies parameter changes by optimizing the filler content to achieve improved impermeability through composition rather than geometry. The specific filler loading (carbon black 2-15 phr, graphite ≥60 phr) modifies the material's intrinsic permeability properties, allowing thinner sections to achieve the same impermeability performance.
Data Source
AI summary
The invention relates to a rubber composition containing at least one elastomer, carbon black in a proportion of 2 to 15 phr, graphite in a proportion of at least 60 phr and a plasticising oil in a proportion not exceeding 30 phr. The composition of the invention is particularly useful as a tyre inner-liner.