Overview
ISO 21915-3:2020 specifies a quantitative laboratory method for blend quantification of cupro and lyocell fibers using infrared (IR) spectroscopy and multivariate analysis. The standard defines how to prepare calibration specimens, measure ATR-IR spectra, build a partial least squares (PLS) calibration model, and predict cupro/lyocell composition in textile samples. This procedure applies only when the sample contains cupro and/or lyocell; other fibres must be identified and removed using ISO/TR 11827 and the relevant parts of the ISO 1833 series.
Key topics and technical requirements
- Measurement technique: Attenuated Total Reflection (ATR) infrared spectroscopy with wave number range 800–3 000 cm−1 and interval 1.0 cm−1.
- Sample preparation: Freeze fibers with liquid nitrogen, pulverize with a cryogenic grinder, blend powders into defined ratios (e.g., 100/0, 80/20, …, 0/100), and mold into tablets (three tablets per blend for calibration).
- Calibration model: Use PLS regression to relate IR absorption data to cupro percentage. Software must support PLS, cross-validation, and calculation of SEC (standard error of calibration), SECV (standard error of cross validation), and coefficient of determination R².
- Optimization & validation: Select number of factors to optimize the calibration. Target performance in this document: SEC ≤ 10, SECV ≤ 10, and R ≥ 0.7 for both calibration and cross-validation.
- Testing procedure: Prepare test sample tablets the same way, measure ATR-IR, input spectra to the calibration model, and report the averaged result from three specimens to 0.1%.
- Reporting: Test report must reference ISO 21915-3:2020, identify the product, show results (cupro/lyocell composition to 0.1), list deviations, observations, and test date.
Applications and users
- Quality control laboratories in the textile and apparel industry performing fiber composition analysis and labeling verification.
- Manufacturers and suppliers validating blends of regenerated cellulose fibres (cupro, lyocell) for product claims and regulatory compliance.
- Independent testing and certification bodies, forensic textile analysts, and R&D groups developing spectral calibration models.
- Useful where traditional chemical tests or visual methods cannot reliably distinguish cupro from lyocell.
Related standards
Keywords: ISO 21915-3:2020, cupro, lyocell, blend quantification, ATR-IR spectroscopy, PLS regression, multivariate analysis, textile fibre analysis, calibration model, SEC, SECV.
Open preview (PDF)Textiles — Qualitative and quantitative analysis of some cellulose fibres (lyocell, cupro) and their blends — Part 3: Blend quantification using spectral analysis method
