Overview
EN ISO 1833-11:2017 - part of the ISO 1833 series on textiles - specifies a quantitative chemical analysis method using sulfuric acid to determine the mass percentage of cellulose fibres (after removal of non‑fibrous matter) in textile mixtures. It applies to mixtures of natural and man‑made cellulose fibres (e.g., cotton, flax, hemp, ramie, viscose, cupro, modal, lyocell) with polymers such as polyester, polypropylene, elastomultiester, elastolefin and polypropylene/polyamide bicomponent. The method is internationally adopted (endorsed by CEN) and supersedes earlier editions.
Key Topics and Requirements
- Principle: Dissolve cellulose fibres from a known dry mass of the specimen in ~75% (mass fraction) sulfuric acid; collect, wash, dry and weigh the insoluble residue; calculate cellulose proportion by difference.
- Reagents:
- Sulfuric acid ~75% (acceptable range 73–77%); preparation example given (dilution from concentrated acid).
- Dilute ammonia solution for neutralizing/washing residue.
- Apparatus & Conditions:
- Conical (glass‑stoppered) flask, min. 500 ml.
- Heating to maintain (50 ± 5) °C for the digestion period.
- Test Procedure Highlights:
- Add 200 ml sulfuric acid per gram of dry specimen.
- Maintain at 50 ± 5 °C for 1 hour, with gentle shaking every ~10 minutes.
- Filter, wash successively with cold water and dilute ammonia, dry and weigh residue.
- Allow wash liquids to drain by gravity before applying suction.
- Calculation:
- Follow general calculation rules in ISO 1833‑1; factor d = 1.00 (except propylene/polyamide bicomponent d = 1.01).
- Precision:
- Confidence limits not greater than ±1 percentage point (95% confidence) on homogeneous mixtures.
Applications and Users
- Practical uses:
- Routine fibre composition testing in textile quality control and manufacturing.
- Verification for labeling, trade compliance and material declarations.
- Laboratory analysis for research, product development and material certification.
- Typical users:
- Textile testing laboratories and accredited conformity assessment bodies.
- Textile manufacturers, mill labs and fiber suppliers.
- Regulatory agencies and quality assurance teams concerned with fibre content.
Note: The method involves concentrated sulfuric acid - appropriate chemical handling, ventilation and laboratory safety procedures are required.
Related Standards
- ISO 1833‑1 - General principles of quantitative chemical testing for textiles (normative reference).
- Other parts of the ISO 1833 series address different fibre mixtures and extraction methods; consult the series for complementary procedures.
