ISO 815-2:2019

Overview

ISO 815-2:2019 - Rubber, vulcanized or thermoplastic - Determination of compression set - Part 2: At low temperatures specifies two standardized test methods for measuring the compression set (permanent deformation after compression) of vulcanized and thermoplastic rubbers when tested at low temperatures. The document defines equipment, specimen preparation, test conditions, procedures and result expression for both methods, and explains why measurements must be made at the test temperature (effects such as glass hardening or crystallization are reversible on warming).

Keywords: ISO 815-2:2019, compression set, low temperatures, rubber testing, vulcanized rubber, thermoplastic rubber.

Key technical topics and requirements

• Two test methods:
  • Method 1: Based on the methodology of ISO 815-1 - compress specimen to a specified strain, maintain at low temperature for a set time, release and measure recovered thickness at the test temperature.
  • Method 2: Uses a specified testing device that measures and records specimen thickness during recovery under a defined pressure; thickness can be recorded at intervals or at a specified recovery time. Because recovery is under load in Method 2, results are not directly correlated with Method 1.
• Test strain by hardness:
  • 25 % (±2 %) for hardness < 80 IRHD
  • 15 % (±2 %) for hardness 80–89 IRHD
  • 10 % (±1 %) for hardness 90–95 IRHD
• Apparatus requirements:
  • Compression plates: flat, highly polished, corrosion-resistant (example surface finish Ra ≤ 0.4 µm noted); plate bending under load ≤ 0.01 mm.
  • Low-temperature cabinet: able to maintain test temperature (mechanical refrigeration, dry ice or liquid nitrogen cooling permitted); design must allow release and measurement without direct contact (glove ports or remote handling).
• Measurement principles: thickness measurements are always taken at the low test temperature because low-temperature effects are reversible on warming.
• Calibration and conditioning: references ISO 18899 and ISO 23529 for calibration and specimen preparation/conditioning.

Practical applications

• Assessing low-temperature performance of rubber components subject to prolonged compression: seals, gaskets, O‑rings, vibration isolators and cold‑climate elastomer parts.
• Material selection, quality control, product specifications and R&D to ensure elastic recovery and serviceability in cold or cryogenic environments.
• Comparative evaluation of formulations where glass transition or crystallization may affect dimensional recovery.

Who uses this standard

• Rubber test laboratories and QC/QA teams
• Rubber compounders and material suppliers
• OEMs in automotive, aerospace, oil & gas, HVAC and cryogenics
• Specification writers and procurement teams requiring validated low-temperature compression set data

Related standards

• ISO 815-1 (general compression set methods)
• ISO 23529 (preparing and conditioning test pieces)
• ISO 18899 (calibration of test equipment)

ISO 815-2:2019 provides a reproducible framework for low-temperature compression set testing, enabling consistent material assessment for cold‑service applications.