ISO 21915-3:2020

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

• ISO 21915 series (other parts: identification and alternative quantification methods such as ISO 21915‑1 and ISO 21915‑2).
• ISO/TR 11827 (qualitative identification of fibers).
• ISO 1833 series (chemical composition separation and quantification methods).

Keywords: ISO 21915-3:2020, cupro, lyocell, blend quantification, ATR-IR spectroscopy, PLS regression, multivariate analysis, textile fibre analysis, calibration model, SEC, SECV.