Overview
EN ISO 1833-25:2020 - Textiles - Quantitative chemical analysis - Part 25 specifies a chemical method to determine the mass percentage of polyester fibres in textile mixtures after removal of non‑fibrous matter. The method uses a trichloroacetic acid/chloroform reagent to dissolve polyester and quantify the remaining fibres. This edition (2020) supersedes the 2013 version and is endorsed by CEN.
Key topics and technical requirements
- Scope: Applies to mixtures of polyester with aramid fibres (except polyamide imide), flame retardant (FR) viscose, and polyacrylate.
- Principle: Dissolve polyester from a known dry mass of the specimen using a trichloroacetic acid/chloroform reagent; collect, wash, dry and weigh the insoluble residue; calculate polyester content by difference.
- Reagents:
- Crystallized trichloroacetic acid/chloroform reagent prepared at a mass ratio 1:1.
- Alternative reagent: 15 g trichloroacetic acid filled to 100 g with chloroform.
- Chloroform specified separately.
- Apparatus: Use general apparatus from ISO 1833-1 plus a glass conical flask (min. 200 ml) with stopper and a weighed filter crucible.
- Test procedure highlights:
- Add 50 ml of reagent per gram of specimen, stopper and shake; allow to stand for 15 minutes, shaking intermittently.
- Decant through a weighed filter crucible, wash with 100 ml reagent, transfer residues using reagent (5.2) and chloroform (5.3).
- Dry, cool and weigh residue; inspect microscopically to confirm complete removal of soluble fibre.
- Calculation: Follow ISO 1833-1 general instructions. The correction factor d = 1.00, except for polyacrylate where d = 1.01.
- Precision: Confidence limits for homogeneous mixtures are ≤ ±1 percentage point at 95% confidence.
- Safety: Chloroform and the reagent are harmful; strict safety precautions and compliance with local health/environment regulations are required.
Applications and users
- Textile testing and quality control laboratories performing quantitative chemical analysis of textiles.
- Manufacturers verifying fibre composition in blended fabrics.
- Certification and standards bodies, forensic textile analysts and R&D groups comparing blend contents.
- Useful when other fibres in the blend are insoluble in common solvents and polyester is the removable component.
Related standards
- ISO 1833-1: General principles for quantitative chemical analysis of textiles.
- ISO 1833-24: Alternative method for polyester mixtures (phenol and tetrachloroethane).
- AATCC Fiber Analysis: Quantitative (referenced as an alternative resource).
Keywords: EN ISO 1833-25:2020, quantitative chemical analysis, textiles, polyester, trichloroacetic acid, chloroform, aramid, FR viscose, polyacrylate, fibre composition, textile testing.
