Weather Strip Rubber Composition for Galvanic Corrosion Prevention
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Solution Overview
Problem
Weather strips with high carbon black content cause galvanic corrosion on car bodies, especially when made of aluminum alloys, and reducing carbon black to increase electrical resistance results in a heavier weather strip due to the use of denser fillers, which contradicts the need for a lighter car body.
Innovation Solution
A weather strip with a rubber composition having a volume resistivity of at least 1.0E+6 Ω·cm and a specific gravity of less than 1.30, achieved by using a combination of carbon black and polymers with specific gravity no more than 1.8 and ethylene content between 70 wt % and 50 wt %, ensuring sufficient strength and extensibility while preventing galvanic corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black is reduced to increase electrical resistance, then galvanic corrosion is prevented, but the weather strip becomes heavier due to use of denser fillers
Solution Approach 1:
The patent uses a composite filler system combining carbon black with lighter white fillers (titanium dioxide, silica, calcium carbonate) to achieve high electrical resistance while maintaining low density. This composite approach allows the weather strip to prevent galvanic corrosion without sacrificing weight efficiency.
Solution Approach 2:
The patent changes the physical and chemical parameters of the rubber composition by controlling carbon black concentration (5-50 parts per 100 parts rubber) and incorporating specific ratios of white fillers with defined specific gravities (1.5-2.5). This parameter optimization achieves volume resistivity of 1.0×10^5 Ω·cm or more while keeping specific gravity below 1.20.
2Reliability
If carbon black is reduced to prevent galvanic corrosion, then electrical resistance increases, but reinforcement effect decreases causing degradation of extruded surface
Solution Approach 1:
The patent employs a composite filler system where carbon black works synergistically with white fillers (titanium dioxide, silica, calcium carbonate) to maintain reinforcement effectiveness even at reduced carbon black levels. This composite approach ensures proper extruded surface quality while achieving the required electrical resistance for corrosion prevention.
Solution Approach 2:
The patent applies different filler types to different functional requirements: carbon black provides reinforcement and basic electrical resistance, while white fillers enhance electrical resistance and contribute to surface quality. This localized functional assignment ensures both extruded surface quality and high electrical resistance are achieved.
3Reliability
If carbon black is reduced to increase electrical resistance, then galvanic corrosion is prevented, but noticeable contraction after extrusion occurs
Solution Approach 1:
The patent uses a composite filler system where the combination of carbon black and white fillers (titanium dioxide, silica, calcium carbonate) provides balanced reinforcement. This composite approach maintains dimensional stability and reduces post-extrusion contraction while achieving the necessary electrical resistance for corrosion prevention.
Solution Approach 2:
The patent optimizes the total filler content and composition parameters, controlling carbon black at 5-50 parts and white fillers at 20-80 parts per 100 parts rubber. This parameter control ensures adequate reinforcement for dimensional stability while achieving high electrical resistance.
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 solution effectively prevents galvanic corrosion on car bodies while maintaining a low specific gravity, ensuring the weather strip is both electrically resistant and lightweight, thus meeting the requirements for a lighter car body.
Implementation Method 1
carbon black-containing rubber members having surface electric resistivity of 1.0E+4 to 1.0E+5 Ω·cm are widely used... rubber member containing less carbon black and having surface electric resistivity of no less than 1.0E+6 Ω·cm, which can substantially prevent rusting on an aluminum alloy member
Data Source
AI summary
A weather strip includes an ethylene-α-olefin-nonconjugated diene copolymer rubber composition having a volume resistivity of no less than 1.0E+6 Ω·cm and having a specific gravity of less than 1.30, the rubber composition including: carbon black in an amount of 40 parts by mass to 140 parts by mass; and at least one polymer having a specific gravity of no more than 1.8 and an ethylene content of no more than 70 wt % and at least one polymer having a specific gravity of no more than 1.8 and an ethylene content of no less than 70 wt % in a collective amount of 5 parts by mass to 50 parts by mass, per 100 parts by mass of an EPDM polymer. At least a mount base of the weather strip, which is to be mounted to a car body, is formed of the rubber composition.