Overview
ISO 20754:2018 - Textiles - Man-made fibres - Determination of shape factors in cross section - specifies laboratory methods to quantify the geometric shape of man‑made fibre cross‑sections. The standard defines how to prepare specimens (microtome or plate methods), capture microscope images, and calculate shape factors, perimeter coefficients, and degree of hollowness using measured radii, areas and perimeters. It is intended for use in fibre characterization, quality control and research.
Key topics and requirements
- Scope: Methods for determination of shape factors in the cross‑section of man‑made fibres.
- Specimen preparation:
- Microtome method (slice thickness exposing fibres at about 20–30 µm) or plate method (stretched bundle through a sample plate).
- Sampling: filaments ~0.5 m cut from a package; staple bundles ~0.5 g.
- Apparatus: measuring microscope with magnification ≥ 400×, minimum resolvable distance 1.5 µm, digital measuring stage; fibre microtome; sample plate (≈70 × 20 × 0.2–0.4 mm); stage micrometer (0.01 mm divisions).
- Testing conditions: ambient laboratory conditions are acceptable; avoid compressed edge sections.
- Image capture and testing: capture clear cross‑section images, exclude damaged or incomplete images; test at least 30 cross‑sections per slide (additional tests if confidence criteria are not met).
- Defined metrics and calculations:
- Shape factor (radius): (R − r) / R × 100% where R = radius of minimum circumscribed circle and r = radius of concentric circle internally tangent to the section.
- Shape factor (cross‑section): area difference expressed as percentage of the minimum circumscribed circle area.
- Coefficient of perimeter: ratio of contour perimeter to circle perimeter for same area.
- Degree of hollowness and coefficient of perimeters of hollowness for hollow fibres.
- Additional specific measurements: contour length, arc radius, angles, and distances.
Applications
- Quality control and dimensional verification in textile manufacturing and fibre extrusion processes.
- Morphological analysis for R&D (fibre cross‑section design, hollow fibre evaluation).
- Comparative testing for fibre identification and specification compliance.
- Input data for fabric performance modeling where cross‑sectional geometry affects mechanical, optical or bulk properties.
Who should use this standard
- Textile testing laboratories and quality assurance teams.
- Fibre manufacturers and process engineers.
- Research scientists working on synthetic fibre morphology.
- Standards developers and conformity assessment bodies.
Related standards
- ISO 2076 (man‑made fibres - generic names) - cited normative reference in ISO 20754:2018.
Keywords: ISO 20754, man-made fibres, fibre cross-section, shape factor, degree of hollowness, measuring microscope, microtome, textile testing.