ISO 1833-25:2020

Overview

ISO 1833-25:2020 specifies a quantitative chemical analysis method to determine the mass percentage of polyester fibres in textile mixtures after removal of non-fibrous matter. The method uses a trichloroacetic acid (TCA) and chloroform reagent to dissolve polyester from blends containing polyester with aramid fibres (except polyamide imide), flame retardant (FR) viscose and polyacrylate. The standard complements the general principles given in ISO 1833-1 and incorporates safety warnings concerning the use of chloroform.

Key Topics

• Principle: Polyester is dissolved from a known dry mass of the mixture using a TCA/chloroform reagent. The insoluble residue is collected, washed, dried, and weighed; polyester content is obtained by difference.
• Reagents: A 1:1 mass ratio solution of crystallized trichloroacetic acid and chloroform is used, plus a secondary solution (15 g trichloroacetic acid filled to 100 g with chloroform) and pure chloroform for washing.
• Apparatus: Use the equipment described in ISO 1833-1 and a glass conical flask (stoppered) of minimum 200 ml capacity.
• Test procedure (high level):
  • Place a known dry specimen mass in the conical flask.
  • Add 50 ml of the TCA/chloroform reagent per gram of specimen, stopper and shake vigorously.
  • Allow to stand for 15 minutes, shaking intermittently.
  • Decant through a pre-weighed filter crucible with suction; wash the flask with reagent (5.2) then chloroform (5.3) to transfer residual fibres.
  • Permit washing liquor to drain by gravity before applying suction; dry, cool and weigh residue.
• Calculation detail: Apply the general calculation rules from ISO 1833-1. The density correction factor d = 1.00 except for polyacrylate where d = 1.01.
• Precision: On homogeneous materials the 95% confidence limits are not greater than ±1 percentage point.
• Safety: Chloroform is harmful; strict adherence to safety and local regulatory requirements is mandatory. The standard notes alternative polyester dissolution methods referenced in the bibliography.

Applications

• Quality control and incoming material inspection for textile manufacturers and converters.
• Verification of composition for labelling and regulatory compliance when polyester is blended with aramid, FR viscose or polyacrylate.
• Laboratory standard method for routine textile composition analysis where the described reagents are appropriate.

Related Standards

• ISO 1833-1: General principles for quantitative chemical analysis of textiles.
• ISO 1833-24: Alternative polyester dissolution method (phenol and tetrachloroethane) referenced in the bibliography.
• AATCC Fiber Analysis: Quantitative (referenced as an alternative resource).

Practical value: ISO 1833-25:2020 provides a repeatable, standard procedure for determining polyester mass percentage in specific blends, delivering reliable results for manufacturing QC, material declaration and compliance testing when performed with appropriate safety controls.