Mechanical Seal Elastomer Composition for LLC and Cold Resistance
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Solution Overview
Problem
Mechanical seals for water pumps face challenges in achieving desired long-life coolant (LLC) resistance, compression set characteristics, cold resistance, and processability due to insufficient hardness and cold resistance of conventional nitrile rubber compositions, particularly under high temperature and pressure conditions.
Innovation Solution
A peroxide vulcanized molded article of hydrogenated nitrile rubber with a bound acrylonitrile content of less than 20% and an iodine number of 20 mg/100 g or less, combined with specific ratios of carbon black, silica, silane-based coupling agents, and titanium oxide filler, to enhance LLC resistance and cold resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nitrile rubber or hydrogenated nitrile rubber is used, then processability and basic sealing function are maintained, but LLC resistance and cold resistance are insufficient
Solution Approach 1:
The patent changes the chemical parameters of the rubber material by specifying hydrogenated nitrile rubber with bound acrylonitrile content of 20-40% and iodine number of 20-70 mg/100g. These parameter changes optimize both LLC resistance and cold resistance while maintaining processability, resolving the contradiction between reliability and ease of manufacture.
Solution Approach 2:
The patent uses composite material formulation by combining hydrogenated nitrile rubber with specific fillers (carbon black, silica, titanium oxide) and coupling agents. This composite approach enhances LLC resistance and cold resistance while the peroxide vulcanization system maintains good processability, thus resolving the technical contradiction.
2Reliability
If nitrile content is increased to improve LLC resistance, then antifreeze performance improves, but cold resistance deteriorates
Solution Approach 1:
The patent optimizes the bound acrylonitrile content to 20-40% and iodine number to 20-70 mg/100g, which balances the chemical composition to achieve both LLC resistance and cold resistance. This parameter optimization resolves the contradiction between antifreeze performance and cold resistance.
Solution Approach 2:
The patent achieves different local properties by controlling the distribution and content of nitrile groups within the rubber matrix. The specific bound AN content range creates local regions with appropriate polarity and flexibility, enabling both LLC resistance and cold resistance simultaneously.
3Reliability
If hardness is increased to maintain sealing gap, then sealing function improves, but compression set characteristics worsen
Solution Approach 1:
The patent uses a composite filler system combining carbon black, silica, and titanium oxide with specific surface areas and proportions. This composite filler structure provides reinforcement for sealing function while the peroxide vulcanization network maintains elasticity and recovery, resolving the contradiction between sealing function and compression set characteristics.
Solution Approach 2:
The patent optimizes the vulcanization parameters by using peroxide curing with specific accelerator systems and curing conditions. This creates an optimized crosslink density that provides both the hardness needed for sealing and the elasticity needed for compression recovery, resolving the technical contradiction.
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 achieves excellent LLC resistance, compression set characteristics, and cold resistance, with a glass transition point below −35° C. after exposure to a 30 volume % LLC aqueous solution at 150° C. for 300 hours, while maintaining high processability and hardness.
Implementation Method 1
peroxide vulcanized molded article of hydrogenated nitrile rubber
Implementation Method 2
silane-based coupling agent
Data Source
AI summary
A sealing member for mechanical seals, which is a peroxide vulcanized molded article of a hydrogenated nitrile rubber having a bound acrylonitrile content of less than 20% and an iodine number of 20 mg/100 g or less. The sealing member for mechanical seals is obtained as a peroxide vulcanized molded article of a hydrogenated nitrile rubber composition comprising 0 to 5 parts by weight of carbon black, 20 to 100 parts by weight of silica, and 0.5 to 3 parts by weight of silane coupling agent, based on 100 parts by weight of hydrogenated nitrile rubber, and preferably further compounding 50 parts by weight or less of titanium oxide non-reinforcing filler. The obtained vulcanized molded article is to provide a sealing member for mechanical seals that can achieve desired LLC resistance, and that has excellent compression set characteristics, cold resistance, processability, hardness, etc.