Overview
ISO 20392:2007 - Thermal‑insulating materials - Determination of compressive creep specifies equipment, procedures and calculation methods for measuring the compressive creep of thermal‑insulation products under defined stress, time and environmental conditions. The standard defines how to prepare specimens, apply constant compressive stress, record deformation over time and extrapolate long‑term deformation (see Annex A).
Key topics and technical requirements
- Scope: Applies to thermal‑insulation products for determining increase in deformation under constant compressive stress (compressive creep).
- Apparatus: Two flat, self‑aligning plates (one movable) to compress the specimen; measuring device (e.g., dial gauge/displacement transducer) with 0.01 mm accuracy; vibration damping and stable base.
- Specimens: Square prism specimens with original product thickness; recommended base sizes include 50×50 mm up to 300×300 mm. Surface flatness and parallelism tolerances are specified; facings/skins retained if used in service.
- Conditioning and test environment: Specimens conditioned ≥24 h under test conditions. Standard test climates include (23 ± 2) °C, (50 ± 10)% RH (alternatives also given).
- Stress selection: Tests at three or more stress levels based on a fraction of compressive strength (σcm) or compressive stress at 10% deformation (σc10). Example factors: 0.15, 0.20, 0.25, 0.30, 0.35.
- Measurement schedule: Initial reading 60 s after load and subsequent readings at a series of logarithmically spaced times (e.g., 0.1 h, 1 h, 5 h, 24 h, 2 d, 4 d, … up to at least 90 days). Readings can continue longer and are extrapolated for long‑term deformation.
- Calculation and reporting: Relative deformation (%) calculated from measured deformation and initial thickness. Plotting in linear/log or log/log formats is required. Annex A describes extrapolation (including use of regression and Findley‑type approaches); Annex B gives a regression example. Test report content is prescribed.
Applications and users
- Who uses it: Test laboratories, thermal‑insulation manufacturers, product developers, quality assurance teams, standards bodies and specifiers involved in insulation selection and certification.
- Practical uses:
- Quantifying long‑term compressive performance of insulation materials (e.g., boards, foams) under sustained loads.
- Supporting product development, quality control and performance declarations.
- Providing data for design decisions where compressive deformation impacts thermal or mechanical performance (pipe supports, flooring, service loads).
Related standards
- ISO 844 - Determination of compression properties of rigid cellular plastics (used for strength/stress references).
- ISO 1923 - Determination of linear dimensions (used for specimen measurement and tolerances).
Keywords: ISO 20392:2007, compressive creep testing, thermal‑insulating materials, compressive stress, long‑term deformation, Findley equation, insulation test methods.
