Cross-Section Shape
Definition
The geometry of a fibre when sliced perpendicular to its length. Round (nylon), trilobal (some carpet polyesters), dogbone (acrylic), kidney-bean (cotton lumen), serrated (viscose rayon). Class-level diagnostic.
- Definition
- Fibre geometry when sliced perpendicular to its length
- Round
- Common in nylon
- Trilobal
- Common in some carpet polyesters
- Evidential level
- Class characteristic, not individualising
Common questions
Why is cross-section shape only a class characteristic rather than individualising?+
Manufacturers deliberately design a fibre's extrusion die to give a specific cross-section for performance reasons such as sheen or bulk, so many fibres from different production runs and even different manufacturers can share the same shape, meaning it narrows the possibilities rather than pointing to one source.
How is cross-section shape actually examined in the lab?+
A fibre is embedded and sliced thin enough to view its cut end under a microscope, since the shape is not visible looking along the fibre's length. The observed shape is then combined with colour, diameter, and chemical composition to build the overall comparison.
Related terms
- Birefringence
- The difference between the highest and lowest refractive indices of an anisotropic mineral, seen as a characteristic interference colour between crossed polars....
- Microspectrophotometry (MSP)
- Visible-range spectrophotometry conducted through a microscope, generating an absorbance curve that fingerprints the dye on a single fibre without destroying it.
- Pyrolysis GC-MS
- Heating a tiny polymer sample (about 1 microgram) to roughly 600 to 800 degrees Celsius in an inert atmosphere, separating the volatile...
- Tape Lift
- Adhesive tape pressed onto a substrate to recover fibres, hairs and other particulates. The standard collection method for fibres on clothing, upholstery...
- Yarn Twist
- The number of turns per unit length and the direction of twist in a yarn. S-twist and Z-twist are the two standard...