Flame-Retardant Rubber Composition for Air Spring Bellows
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Solution Overview
Problem
Articles made from elastomeric mixtures, such as air spring bellows and vibration dampers, fail to meet stricter fire safety standards due to high heat release rates and toxic smoke production, while traditional flame retardants impair physical properties like hardness, essential for dynamic applications.
Innovation Solution
A single- or multi-layered article with a rubber mixture containing carbon black with specific surface area and oil absorption properties, combined with different particle sizes of aluminum trihydrate, and additional flame retardants, optimizing fire safety without compromising hardness and dynamic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional flame retardant substances are incorporated into elastomeric mixtures to improve fire safety, then fire behavior is improved, but physical properties such as hardness are impaired
Solution Approach 1:
The invention changes the particle size parameter of aluminum trihydrate from conventional larger sizes to fine particles with d50 between 0.5-2.0 μm. This parameter change allows the flame retardant to effectively improve fire safety while minimizing the impairment of hardness and other physical properties, as the fine particles distribute more uniformly and require smaller loading amounts to achieve the same fire protection effect.
Solution Approach 2:
The invention uses a composite approach by combining fine aluminum trihydrate particles with specific carbon black types (N-339 or N-550) in defined ratios. This composite material strategy synergistically improves fire safety through the aluminum trihydrate while the carbon black reinforces the rubber matrix, thereby maintaining hardness and physical properties that would otherwise be compromised by flame retardant addition.
2Strength
If elastomeric mixtures based on NR and/or IR are used to achieve good elastic properties, then cushioning and vibration properties are improved, but heat release rate in combustion is high
Solution Approach 1:
The invention introduces fine aluminum trihydrate particles as an intermediary substance that interferes with the combustion process of the elastomeric mixture. These particles act as a barrier between the fuel (elastomer) and oxygen, and also serve as a heat sink due to their endothermic decomposition, thereby reducing the heat release rate while allowing the natural rubber or polyisoprene base to maintain its excellent elastic properties.
3Reliability
If elastomeric mixtures based on CR are used to achieve good resistance to weathering and heat, then durability is improved, but smoke toxicity in combustion is high
Solution Approach 1:
The invention converts the potential harm of chloroprene rubber combustion into a benefit by using fine aluminum trihydrate particles that decompose endothermically during combustion. This decomposition process absorbs heat and releases water vapor, which dilutes and neutralizes the toxic smoke products generated by CR combustion, thereby transforming a harmful combustion characteristic into a safer scenario while preserving the excellent weathering and heat resistance of CR.
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 combination of finely divided carbon blacks with different aluminum trihydrate types significantly improves fire behavior, reducing the need for additional flame retardants and maintaining essential physical properties, enabling compliance with stricter fire safety standards like EN-45545 without sacrificing performance.
Implementation Method 1
at least one carbon black having a BET surface area according to DIN-ISO 9277 between 35 and 140 m2/g and an oil absorption number (OAN) according to ISO 4656 between 70 and 140 ml/100 g
Implementation Method 2
a first aluminum trihydrate (ATH_1) and at least one further aluminum trihydrate (ATH_2), wherein the first aluminum trihydrate (ATH1) and the further aluminum trihydrate (ATH2) each have a different particle size
Data Source
AI summary
The invention relates to an article having a single- or multi-layered main body having elastic properties, in particular an air spring bellows, a metal-rubber element or a vibration damper.In order to improve its flame retardant properties, the main body of the article consists of or contains at least one layer D constructed from a rubber mixture which is free from halogen-containing flame retardants and contains at least one carbon black having a BET surface area according to DIN-ISO 9277 between 35 and 140 m2/g and an oil absorption number (OAN) according to ISO 4656 between 70 and 140 ml/100 g and a first aluminum trihydrate (ATH_1) and at least a further aluminum trihydrate (ATH_2), wherein the first aluminum trihydrate (ATH_1) and the further aluminum trihydrate (ATH_2) each have a different particle size.