ASTM D395-18 (2025) PDF

Full title and description

ASTM D395-18 (2025) — Standard Test Methods for Rubber Property—Compression Set. This standard specifies procedures for measuring the permanent deformation (compression set) of vulcanized rubber and similar elastomers after exposure to compressive stress in air or liquid media; it provides three test methods to simulate common service modes (constant force, constant deflection, and deflection adjusted for material hardness).

Abstract

ASTM D395-18(2025) defines laboratory methods to determine how well rubber retains elastic recovery following prolonged compression. It covers specimen preparation, apparatus, test conditions (temperatures and durations), measurement and calculation of compression set, and reporting. The standard is intended for materials used in seals, gaskets, vibration isolators and other components subjected to compressive stresses.

General information

• Status: Current / Active (reaffirmed/updated in February 2025).
• Publication date: February 2025 (publication listed as Feb 1, 2025; ASTM activity noted Feb 21, 2025).
• Publisher: ASTM International (American Society for Testing and Materials).
• ICS / categories: 83.060 (Rubber) — Rubber and plastics industries; related to rubber testing and rubber products.
• Edition / version: D395-18, reissued/reconfirmed as D395-18(2025).
• Number of pages: 8 pages (concise test-method standard).

Scope

These test methods cover the testing of rubber intended for use in applications in which the rubber will be subjected to compressive stresses in air or liquid media. The standard provides three specific test methods: Method A — Compression Set Under Constant Force in Air; Method B — Compression Set Under Constant Deflection in Air (the default unless otherwise specified); and Method C — Compression Set Under Constant Deflection in Air Considering Material Hardness. Method B is not suitable for vulcanizates harder than 90 IRHD. Results are reported as percent compression set and are used for material specification, quality control and comparative performance assessment.

Key topics and requirements

• Three test methods: Method A (constant force), Method B (constant deflection — default), and Method C (deflection adjusted by hardness).
• Specimen types and dimensions (standard button/disc specimens or as specified), conditioning, and required thickness/spacer dimensions for constant-deflection tests.
• Specified test temperatures and durations to simulate service conditions (common elevated-temperature exposures and standard time intervals; test and recovery intervals defined for repeatable measurement).
• Measurement procedure: remove compressive load, allow a standard recovery period, measure final thickness and calculate compression set as a percentage of original deflection or spacer geometry.
• Reporting and limits: include test method used, specimen details, temperature and duration, measured dimensions, calculated compression set, and any deviations from the procedure.
• Applicability notes: Method B is unsuitable for materials harder than 90 IRHD; selection of method should match the intended service conditions.

Typical use and users

Common users include rubber compounders, OEMs (automotive, aerospace, industrial equipment), test laboratories and quality/assurance engineers. Typical uses are material acceptance testing, batch quality control, R&D comparisons of formulations, specification compliance for seals and gaskets, and failure analysis when permanent set contributes to loss of function.

Related standards

ASTM D395 is commonly used alongside other rubber test standards such as ISO 815 (compression set — international equivalent/methods), ASTM D2240 (durometer hardness), ASTM D412 (tensile properties), ISO 188 (heat aging) and other ASTM/ISO tests addressing dimensional stability, fluid resistance and mechanical properties used to characterize elastomers for sealing and damping applications.

Keywords

compression set; compression set A; compression set B; compression set C; constant force; constant deflection; elastomer recovery; rubber testing; seals; gaskets; ASTM D395; IRHD hardness.

FAQ

Q: What is this standard?

A: ASTM D395-18(2025) is the ASTM standard that defines laboratory test methods for measuring the compression set (permanent deformation after compression) of vulcanized rubber and similar elastomers.

Q: What does it cover?

A: It covers specimen preparation, apparatus, three test methods (A, B and C), test conditions (temperature and exposure time), measurement after recovery, calculation of percent compression set, and reporting requirements for results intended to represent static compressive-service behavior in air or liquids.

Q: Who typically uses it?

A: Material suppliers, product designers, QA/QC laboratories, independent testing houses, and R&D teams in industries that rely on rubber seals, gaskets, mountings and vibration-damping components.

Q: Is it current or superseded?

A: It is current and active as of February 2025. The document is D395-18 reissued/reconfirmed with activity recorded in February 2025; users should check ASTM or their national standards provider to confirm any amendments or errata after that date.

Q: Is it part of a series?

A: Yes — it belongs to the family of ASTM D standards for rubber properties (developed by ASTM subcommittee D11.10) and is frequently used in combination with other ASTM/ISO test methods for comprehensive elastomer characterization.

Q: What are the key keywords?

A: compression set, constant deflection, constant force, elastomer recovery, rubber testing, seals, gaskets, IRHD, ASTM D395.