Overview
EN ISO 1890:2009 - Reinforcement yarns: Determination of twist specifies a standardized method to measure twist in yarns made from reinforcement fibres such as textile glass, carbon, aramid or other reinforcement fibres. The method measures the number of turns required to remove twist from a specimen and expresses twist as turns per metre. It applies to single yarns and to folded or cabled yarns (generally applied to the final twist step). The procedure is intended for package‑wound yarns; measurements taken from beams, warps or fabrics are indicative only. The method is not applicable to products made from staple fibres.
Key topics and requirements
- Principle: Remove twist by untwisting one end until filaments are parallel; record the number of turns N required for a specimen length L and calculate T = N / L (turns per metre).
- Specimens: Measurements are based on three consecutive specimens from an elementary unit or laboratory sample (more if specified by the purchaser/specification).
- Apparatus: A twist tester with two clamps (one rotating, one sliding), a counter capable of reading to the nearest turn, and a length measurement device accurate to ±1 mm. A dissection needle or thin blade and magnifier are used to verify complete untwisting.
- Dimensions & tension:
- Initial clamp separation: 500 mm ± 1 mm.
- Recommended yarn tension (if applied): 0.25 cN/tex ± 0.1 cN/tex (can be omitted for routine checks, ensuring the yarn is just taut).
- Special provision for low-twist carbon yarns: longer specimen lengths (4–5 m) may be used with appropriate length accuracy.
- Take‑off influence: The standard uses a tangential take‑off basis. Over‑end take‑off alters measured twist depending on bobbin circumference; EN ISO 1890:2009 provides guidance and a correction relation based on bobbin diameter.
- Conditioning: No conditioning required for routine testing; in disputes use standard atmosphere per ISO 291.
- Reporting: Results must include reference to EN ISO 1890:2009, yarn identification, sampling procedure, specimen length, twist direction (Z or S) and value, any deviations and date of test.
- Precision: Interlaboratory precision data are not available (precision unknown).
Applications and users
- Quality control and acceptance testing for manufacturers and suppliers of reinforcement yarns (glass, carbon, aramid).
- Composite part producers, prepreg and filament‑winding operations, textile labs and testing houses needing verified twist data for processing, handling and performance consistency.
- R&D and standards teams verifying twist for product specifications or comparative testing.
Related standards
- ISO 2:1973 - Direction of twist (Z/S) designation
- ISO 291 - Standard atmospheres for conditioning and testing
- ISO 1889 - Determination of linear density (referenced when linear density is unknown)
Keywords: EN ISO 1890:2009, ISO 1890:2009, reinforcement yarns, determination of twist, twist measurement, twist tester, glass fibre yarn, carbon fibre yarn, aramid yarn, cabled yarn, package-wound yarn.
