SIST EN 3698:2014

Overview

SIST EN 3698:2014 specifies the requirements and properties for acrylonitrile-butadiene rubber (NBR) with low temperature resistance and a hardness of 70 IRHD, tailored for aerospace applications. Developed under the Aerospace Series standards by SIST and harmonized with European norms, this standard ensures that NBR materials offer the durability and performance required in demanding aerospace environments. The document provides guidance on material properties, testing methods, designation, and technical specifications, ensuring reliable performance in applications where exposure to low temperatures and petroleum-based fluids is common.

Key Topics

• Material Properties: The standard details physical and mechanical properties for NBR, including hardness (70 IRHD), tensile strength, elongation at break, density, resistance to low temperatures, compression set, ozone resistance, and performance after exposure to oils and fuels.
• Temperature Resistance: Specifies suitable temperature ranges for continuous (−45°C to 110°C) and intermittent (up to 130°C) service, making NBR ideal for components exposed to extreme thermal conditions.
• Suitability for Aerospace Applications: Emphasizes the material’s compatibility with petroleum-based fuels and lubricants, vital for aerospace systems.
• Testing Methods: Sets forth standard laboratory tests for qualification and batch acceptance, referencing related standards such as EN 3207 and ISO 1817 to determine compliance.
• Designation and Labelling: Outlines proper designation of the rubber to ensure traceability and standardization across the aerospace supply chain.

Applications

Acrylonitrile-butadiene rubber (NBR) conforming to SIST EN 3698:2014 is primarily used in:

• Seals and O-rings: Suited for hydraulic and fuel systems in aircraft, where low temperature flexibility and resistance to fuel and oil are critical.
• Gaskets and Elastomeric Components: Used in aerospace assemblies exposed to temperature cycling and chemical interaction with petroleum products.
• Flexible Connectors and Hoses: Protects against wear and fluid penetration while maintaining integrity at low temperatures.
• General Aerospace Elastomeric Parts: Any application requiring high reliability and compliance with international standards for performance and safety.

NBR to this standard ensures consistent quality and predictable behavior, reducing the risk of failure in vital aerospace systems.

Related Standards

Organizations adhere to additional standards to ensure comprehensive performance and compatibility:

• EN 3207: Aerospace series - Rubber compounds - Technical specification, referenced for further technical requirements and validation procedures.
• ISO 1629: Rubber and latices – Nomenclature, essential for the correct identification of rubber materials.
• ISO 1817: Rubber, vulcanized – Determination of the effect of liquids, provides test methods for assessing chemical resistance.

By harmonizing with these standards, SIST EN 3698:2014 supports interoperability and safety in aerospace manufacturing and maintenance.

Practical Value

Implementing SIST EN 3698:2014 enables manufacturers, suppliers, and maintenance organizations to:

• Achieve consistent quality in aerospace rubber components.
• Ensure compliance with international and European aerospace requirements.
• Improve the reliability and safety of aircraft systems exposed to challenging operational environments.
• Streamline procurement and certification processes through standardized material specifications.

Meeting these standards contributes directly to the long-term performance and safety of aerospace vehicles, safeguarding both assets and crew.