GB/T 6509-2025 Determination of caprolactam and oligomers content in polycaprolactam (PA6) chip and fibre English, Anglais, Englisch, Inglés, えいご
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ICS 59.060.20 CCS W 50
People's Republic of China National Standard
GB/T 6509-2025 Replaces GB/T 6509-2005
Determination of caprolactam and oligomers content inpolyeaprolactam(PA6)chip and fibre
Issued data:2025-08-29 Implemented data:2026-03-01
Issued by State Administration for Market Regulation, Standardization Administration of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Method A—High-Performance Liquid Chromatography
5 Method B—Acid Hydrolysis Spectrophotometry
6 Method C—Redox Titration
7 Test Report
Determination of Caprolactam and Oligomers Content in Polycaprolactam (PA6) Chips and Fibers
WARNING: Personnel using this document should have practical experience in laboratory work. This document does not address all potential safety issues. Users are responsible for implementing appropriate safety and health measures and ensuring compliance with national regulations.
1 Scope
This document describes methods for determining caprolactam and oligomers content in polycaprolactam (PA6) chips and fibers.
Method A (High-Performance Liquid Chromatography) is applicable to polycaprolactam chips and polycaprolactam fibers (Nylon 6), and other PA6 products may be referenced. Method B (Acid Hydrolysis Spectrophotometry) is applicable to polycaprolactam fibers (Nylon 6). Method C (Redox Titration) is applicable to fiber-grade polycaprolactam chips and may also be used for rapid determination of caprolactam and oligomers in polycaprolactam fibers within enterprises.
2 Normative References
The following documents contain provisions that, through reference in this text, constitute essential requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 4146 (All parts) Textiles—Chemical Fibers
GB/T 6682 Specification and Test Methods for Water for Analytical Laboratory Use
3 Terms and Definitions
Terms and definitions established in GB/T 4146 (All parts) and the following apply to this document.
3.1 Polycaprolactam (PA6)
Chemical formula: (C₆H₁₁NO)n, a polyamide formed by ring-opening polymerization of caprolactam.
Note: Its resin chips are called polycaprolactam chips; if spun into fibers, they are called polycaprolactam fibers, also known as Nylon 6.
3.2 Caprolactam
A monomer used for the production of polycaprolactam (PA6).
Note: Residual in polycaprolactam (PA6) chips or fibers.
3.3 Oligomer
Oligomers with a degree of polymerization less than 10 present in polycaprolactam (PA6) chips or fibers.
4 Method A—High-Performance Liquid Chromatography
4.1 Principle
The polycaprolactam (PA6) chip or fiber sample is dissolved in a solvent (hexafluoroisopropanol), and the large molecules in the sample solution are precipitated using methanol as a precipitating agent. The caprolactam and its cyclic oligomers in the sample solution are separated and determined using an ultra-high-performance liquid chromatograph or high-performance liquid chromatograph (see Appendix A). The components are qualitatively identified by retention time and ultraviolet spectrum, and quantitatively analyzed using external standard method.
4.2 Reagents or Materials
Unless otherwise specified, only chromatographic-grade reagents are used.
4.2.1 Water: GB/T 6682, Grade 2.
4.2.2 Hexafluoroisopropanol: CAS No. 920-66-1, purity ≥99.5%.
4.2.3 Methanol: CAS No. 67-56-1.
4.2.4 Acetonitrile: CAS No. 75-05-8.
4.2.5 Caprolactam reference material: CAS No. 105-60-2, purity ≥99.5%.
4.2.6 Caprolactam cyclic oligomer reference material or reference substance: purity ≥95%; preparation method for caprolactam cyclic oligomer reference substance is provided in Appendix B.
4.2.7 Parafilm.
4.3 Instruments and Equipment
4.3.1 Ultra-high-performance liquid chromatograph or high-performance liquid chromatograph: equipped with a diode array detector or ultraviolet detector.
4.3.2 Volumetric flask: 25 mL, 250 mL.
4.3.3 Polytetrafluoroethylene syringe filter: hydrophobic, pore size ≤0.22 μm.
4.3.4 Electronic balance: readability 0.1 mg.
4.3.5 Constant-temperature shaking water bath: temperature control accuracy ±2℃.
4.4 Test Procedure
4.4.1 Chromatographic Reference Conditions
4.4.1.1 Ultra-High-Performance Liquid Chromatograph Chromatographic Reference Conditions
Column: C18 column, 2.1 mm × 100 mm, 1.7 μm (or equivalent). Mobile phase A: 0.1% trifluoroacetic acid aqueous solution. Mobile phase B: acetonitrile. Gradient elution program: 0–2 min, 5% B; 2–10 min, 5–30% B; 10–12 min, 30–50% B; 12–14 min, 50–100% B; 14–16 min, 100% B; 16–17 min, 100–5% B; 17–20 min, 5% B. Flow rate: 0.3 mL/min. Column temperature: 30℃. Detection wavelength: 210 nm. Injection volume: 2 μL.
