Overview
ISO 9866-2:1991 - Textiles: Effect of dry heat on fabrics under low pressure - Part 2 specifies a laboratory test method to determine dimensional change of fabrics exposed to dry heat under low pressure. The standard defines the principle, apparatus, conditioning and test atmospheres, specimen preparation, test procedure and the required contents of the test report. Its primary aim is to help predict fabric behaviour in dry-heat manufacturing processes such as fusing and heat-transfer printing.
Key topics and technical requirements
- Scope & principle: Two fabric specimens are exposed to a defined dry-heat, low-pressure treatment and dimensional changes are measured before and after exposure.
- Specimen preparation: Cut two non-creased specimens (edges parallel to warp/weft) - overall dimensions: 240 mm by 290 mm. Avoid cutting from fabric ends/selvages.
- Apparatus:
- Press as specified in ISO 9866-1 (work area larger than specimen).
- Ruler ≥750 mm with mm scale; flexible steel tape or fiberglass tape for garments.
- Marking means: indelible ink, contrasting fine threads, heated pin (for thermoplastics) or staples.
- Flat table and equipment to generate conditioning/test atmospheres (per ISO 139).
- Atmospheres and conditioning:
- Preconditioning: humidity ≤10% RH and temperature ≤50 °C.
- Conditioning/testing atmosphere (per ISO 139): (65 ± 2)% RH at (20 ± 2) °C or (27 ± 2) °C.
- Condition the specimen flat for 4 h or until thermal equilibrium is reached.
- Test exposure (used unless otherwise specified): examples from ISO 9866-1: temperature 150 °C, pressure 0.3 kPa, duration 20 s (see ISO 9866-1 for exact press conditions).
- Measurement & accuracy: Measure points AB, CD, EF, GH to ±0.5 mm. Calculate percentage dimensional change using the standard formula: (h − l0) / l0 × 100, where l0 is the initial (preconditioned) dimension and h is the post-treatment dimension.
- Report requirements: include standard reference (ISO 9866-2:1991), sample ID, any deviations from prescribed conditions, mean dimensional changes (and intermediate-stage changes if applicable), and any appearance changes.
Applications and users
- Textile test laboratories performing fabric testing and quality control.
- Apparel and technical textile manufacturers assessing dimensional stability for processes such as fusing, ironing, and heat-transfer printing.
- R&D teams developing finishes and heat-sensitive coatings.
- Compliance and standards teams documenting shrinkage and process acceptance criteria.
Related standards
- ISO 9866-1:1991 - Part 1: Procedure for dry-heat treatment of fabrics
- ISO 139 - Conditioning and test atmospheres for textiles
- ISO 3759 - Specimen preparation, marking and measuring for dimensional tests
Keywords: ISO 9866-2:1991, textiles, dry heat, low pressure, dimensional change, fabric testing, dimensional stability, textile testing method, conditioning atmospheres, quality control.