Crosslinkable Rubber Composition for Radiator Metal Adhesion
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Solution Overview
Problem
Carboxyl group-containing highly saturated nitrile copolymer rubber crosslinked products do not maintain satisfactory metal adhesion when immersed in Longlife coolant (LLC), which is a critical issue for applications like automobile radiators.
Innovation Solution
A crosslinkable rubber composition comprising a carboxyl group-containing nitrile rubber with a halogen or halogen compound, a polyamine-based crosslinking agent, and a metal-based acid acceptor selected from Group 2, 12, or 13 metal oxides, hydroxides, or hydrotalcites, which enhances compression set resistance and maintains metal adhesion even after immersion in LLC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carboxyl group-containing highly saturated nitrile copolymer rubber is used for crosslinking, then compression set resistance is improved, but metal adhesion deteriorates when immersed in LLC
Solution Approach 1:
A zinc oxide-based metal-based acid acceptor is introduced as an intermediary substance between the rubber and metal. This mediator captures harmful carboxylic acid generated during crosslinking and prevents it from attacking the metal interface, thereby maintaining metal adhesion while preserving compression set resistance
Solution Approach 2:
The carboxylic acid byproduct of crosslinking, which normally causes metal adhesion deterioration, is converted into a beneficial effect by using metal-based acid acceptors to capture it. The captured acid forms stable salts that actually enhance the crosslinking network and improve compression set resistance without harming metal adhesion
2Temperature
If crosslinking is performed to improve compression set resistance, then heat resistance is improved, but metal adhesion under LLC immersion deteriorates
Solution Approach 1:
Metal-based acid acceptors serve as intermediary substances that protect the metal-rubber interface from the harmful effects of crosslinking byproducts. They capture carboxylic acid generated during crosslinking, preventing metal adhesion deterioration while allowing the crosslinking network to develop full heat resistance
Solution Approach 2:
The chemical environment at the metal interface is changed by introducing metal-based acid acceptors. This parameter change (pH control through acid capture) prevents the degradation of metal adhesion while maintaining the thermal stability provided by crosslinking
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 rubber crosslinked product exhibits excellent compression set resistance and maintains strong metal adhesion after being immersed in LLC, making it suitable for various applications including automobile radiators and machine tools.
Implementation Method 1
a polyamine-based crosslinking agent (B)... a rubber crosslinked product obtained thus exhibits excellent heat resistance
Implementation Method 2
a metal-based acid acceptor (C) selected from oxides of metals belonging to Group 2, 12 or 13 of the Periodic Table, hydroxides of metals belonging to Group 13 of the Periodic Table, hydrotalcites
Data Source
AI summary
A disclosed crosslinkable rubber composition includes a carboxyl group-containing nitrile rubber (A) containing a halogen or a halogen compound, and having an iodine value of 120 or less; a polyamine-based crosslinking agent (B); and a metal-based acid acceptor (C).