Overview
ISO 16985:2003 - "Wood‑based panels - Determination of dimensional changes associated with changes in relative humidity" - specifies a laboratory method to quantify how wood‑based panels change in length and thickness when exposed to different relative humidity (RH) conditions. The method captures hygroscopic behaviour and hysteresis by conditioning specimens through defined climates and measuring dimensional and mass changes. This standard is based on EN 318 and complements related ISO methods for moisture content and sampling.
Key topics and requirements
- Scope: Measures dimensional changes (length and thickness) of wood‑based panels due to RH variations.
- Specimens: Dimensions (300 ± 1) mm × (50 ± 1) mm × t (panel thickness). Two sets of four specimens are taken in each panel direction (see ISO 16999 for sampling).
- Conditioning climates: Specimens are conditioned at 20 °C under three RH levels:
- Set 1: 30% → 65% → 85% RH
- Set 2: 85% → 65% → 30% RH
This captures adsorption and desorption hysteresis; mass is held to constant (two weighings 24 h apart differ ≤ 0.1%).
- Apparatus and tolerances:
- Climate chambers: ±1 °C temperature, ±3% RH
- Hygrometer: ±1% RH; thermometer: ±0.5 °C
- Length/thickness instruments: precision ±0.01 mm
- Balance as per ISO 16979
- Measurement rules:
- Measure length (between reference marks), thickness at three central points, and mass after conditioning steps 2 and 3; measurements in conditioning atmosphere or within 5 minutes of removal.
- Calibration using a non‑corroding gauge bar (known to 0.01 mm).
- Calculations and reporting:
- Compute relative length change (mm/m) between 65%↔85% and 65%↔30% RH using specified equations; thickness change expressed as percent.
- Report mean and standard deviation per panel, moisture content (ISO 16979), and full test details. Note: ISO 16979 may not be suitable for cement‑bonded particleboards.
Applications and users
- Who uses ISO 16985: test laboratories, manufacturers of MDF, particleboard, plywood, flooring and furniture components, product development teams, and quality assurance/standards compliance personnel.
- Practical applications:
- Establishing dimensional stability specifications for wood‑based panels.
- Quality control and batch acceptance testing.
- Comparing formulations, adhesives, coatings, or treatments that affect moisture response.
- Supporting product datasheets, performance claims, and design tolerances for installation and end‑use environments.
- Research into hygroscopic behaviour and microstructural effects on swelling/shrinkage.
Related standards
- ISO 16979 - Wood‑based panels - Determination of moisture content
- ISO 16999 - Wood‑based panels - Sampling and preparation of test specimens
- EN 318 - European standard on dimensional changes of wood‑based panels (basis for ISO 16985)
Keywords: ISO 16985:2003, wood-based panels, dimensional changes, relative humidity, dimensional stability, hygroscopic, climate conditioning, panel testing, ISO 16979, ISO 16999.
