Tenacity
Also searched as: specific strength, breaking tenacity, cN/tex, g/den, grams per denier, gf/tex
The breaking force of a fiber or yarn divided by its linear density, a mass-normalized strength usually expressed in centinewtons per tex or grams-force per denier.
In detail
Because fibers and yarns are too fine and irregular to measure cross-sectional area easily, textile strength is normalized by linear density, mass per length, instead of by area. A single fiber or yarn is clamped and extended at a controlled rate until it breaks; the peak force divided by its tex or denier gives tenacity. This lets fibers of very different fineness be compared on one scale. Tenacity is measured on conditioned samples, and many fibers are also tested wet, since water weakens some fibers markedly and affects others little.
The science and numbers
Arithmetic links the units: 1 gram-force is 9.807 mN and 1 denier is 1/9 tex, so 1 gf/den = 9.807 x 9 mN/tex, about 88.3 mN/tex or 8.83 cN/tex, and 1 gf/tex is about 0.98 cN/tex. Stress in megapascals equals tenacity in N/tex times density in g/cm3 times 1,000, so 1 cN/tex corresponds to 10 x density MPa; for PET (about 1.38 g/cm3), 50 cN/tex is roughly 690 MPa. Tenacity rises with the molecular orientation produced by drawing and falls when fillers are compounded into the polymer. Published values show the spread: one comparison reported lyocell at about 32 cN/tex dry and 29 wet, viscose loses close to half its tenacity when wet, and an enzyme-treated sisal fiber reached about 38 cN/tex.
A practical example
Two yarns break at the same force, but one weighs twice as much per kilometer. Dividing each breaking force by its tex shows the lighter yarn has twice the tenacity, meaning its material is stronger for its mass. A designer choosing a lightweight but durable sailcloth yarn would compare tenacity rather than raw breaking force.
What to distinguish
Tenacity is not the same as tensile stress in pascals, which divides force by area; converting between them requires fiber density. It also differs from breaking force, which depends on how much material is present. Tenacity depends on test conditions such as gauge length, extension rate, humidity and whether the sample is wet, so values from different methods are not directly comparable.
Origins and history
Textile strength has long been normalized by linear density because fine, irregular fibers make cross-sectional area hard to measure. Grams per denier followed from the denier count used for silk and filament yarns. The tex system, described by A. G. Scroggie in Textile Research Journal in 1958 and later published by ISO as ISO 1144, gave a metric base, and centinewtons per tex became the usual SI expression, although grams per denier remains common in filament trades.
Related terms
Sources & further reading
- Materials: Melt-spun fibers for textile applications (Hufenus et al., 2020)
- International Journal of Biological Macromolecules: Enzymatic modification of sisal fiber for spinnable textile fibers (2025)
- ISO: ISO 1144:2016 Universal system for designating linear density (Tex System)
- Textile Research Journal: The Tex Universal Yarn Numbering System (Scroggie, 1958)
Technical references reviewed 2026-09-22. Examples are illustrative. Industry organizations and manufacturers describe their own fields; their references are not independent product endorsements. Figures are approximate and depend on the stated test conditions.