ISO 3384-1:2024

Overview

ISO 3384-1:2024 - Rubber, vulcanized or thermoplastic - Determination of stress relaxation in compression - Part 1: Testing at constant temperature specifies standardized procedures to measure how the compressive counterforce from a rubber test piece decreases with time when held at a constant deformation and temperature. The standard covers two measurement approaches (continuous and discontinuous) and two test methods (Method A and Method B), and it applies to both vulcanized and thermoplastic rubber test pieces.

Key topics and requirements

• Test objective: Determine compression stress relaxation R(t) - the percentage reduction in compressive force over time after constant strain is applied.
• Methods:
  • Method A: Compression and all force measurements performed at the specified test temperature.
  • Method B: Compression and measurements performed at standard laboratory temperature after storage at the test temperature. Results differ between methods because Method B includes material shrinkage during cooling.
• Measurement types:
  • Continuous measurement systems (real-time force recording).
  • Discontinuous measurement systems (periodic, interval measurements).
• Test piece geometry: Two shapes are specified - cylindrical test pieces and rings. Results are comparable only for test pieces of similar size and shape. Ring pieces are especially suitable for tests in liquid environments.
• Apparatus and accuracy: Compression plates must be parallel, highly polished (surface finish ≈ Ra 0.4 µm recommended), and rigid (plate bending limits ≤ 0.01 mm under load). Gap variation limits: ±0.01 mm (discontinuous jigs) and ±0.1 mm (continuous rigs). Force measurement accuracy of 1% is required.
• Environment and temperature: Testing at constant ambient or elevated temperatures is specified. Low-temperature testing below standard laboratory temperature is not covered (reliability not proven).
• Supporting requirements: Includes calibration guidance, conditioning of test pieces, measurement of dimensions, duration/immersion liquid options, precision data, and test reporting requirements. Annexes include precision data and a calibration schedule.

Applications and users

ISO 3384-1:2024 is used by:

• Test laboratories and quality control teams assessing sealing force retention and long-term compressive performance.
• R&D teams developing rubber seals, gaskets, O-rings, mounts and vibration-control components.
• Automotive, aerospace, oil & gas, and industrial manufacturers that require verified compression relaxation data for material selection and lifetime assessments.
• Suppliers validating material behavior in gaseous or liquid environments (rings are preferred for immersion testing).

Practical benefits include standardized, comparable stress-relaxation data to support design decisions, service-life estimates, and contractual specifications.

Related standards

• ISO 188 - Accelerated ageing and heat resistance tests for rubber
• ISO 18899 - Guide to calibration of test equipment
• ISO 23529 - Preparation and conditioning of test pieces for physical tests

Keywords: ISO 3384-1:2024, stress relaxation, compression testing, vulcanized rubber, thermoplastic rubber, Method A, Method B, continuous measurement, ring test pieces, cylindrical test pieces.