ISO 9073-3 Strip Tensile Testing of Nonwovens

What the test does

A strip of nonwoven is cut to one of two widths — 25 mm under Option A or 50 mm under Option B — conditioned in the standard atmosphere or prepared wet, and clamped across its full width in a constant rate of extension machine. It is then extended to break, and the maximum force and the elongation at break are recorded. Machine and cross-machine directions are tested and reported separately, and the option used is stated with every value, because results from the two widths are not comparable with one another.

What it measures, and why it matters

How much load a nonwoven web carries before it comes apart, and how far it stretches getting there. Both matter in use: a wipe or a medical drape has to survive handling, and a filter medium has to survive the pressure differential across it. The strip geometry is what makes the number interpretable — the full width is clamped, so every fibre in the section is loaded, and the result belongs to a defined width rather than to whatever portion of the material the grips happened to recruit. The figure is a force for that width, not a stress, because a lofty web's thickness depends mostly on how hard it is measured.

Two options

Option A is 25 mm wide, Option B is 50 mm. They are alternatives, not a progression, and the results are not comparable.

Option A

25 mm specimen width

Option B

50 mm specimen widthThe wider option suits light or open webs where a 25 mm strip has too few bonds in section to be representative.

Machine type

Constant rate of extension

States

Conditioned and wetHygiene and medical nonwovens are used wet, and many lose most of their strength when they are.

Directions

Machine and cross-machine, separatelyA nonwoven laid on a moving belt is strongly oriented by the process itself.

Cut specimens with a sharp die or template

Not with scissorsDakA ragged edge on a nonwoven is a starting notch, and there are no yarns to arrest a tear once it begins.

Nonwovens are not weaves. There is no yarn to redistribute load around a flaw, so edge quality and specimen width matter more here than they do on a woven fabric.

Test speed

Rate — Option B (50 mm strip)

100 mm/min, on a 200 mm gaugeRate held to ±10 %, gauge to ±1 mm. This is the rate carried unchanged from the first edition.

Rate — Option A (25 mm strip)

300 mm/min, on a 75 mm gaugeThe method's second specified rate, paired with its shorter gauge.

Reported

Maximum force and elongation at break

Option

A or B, always statedA result without the option named cannot be compared with anything.

Reject jaw breaks

And record how manyDak

What the machine must be capable of

Small forces, measured properly, at one of two speeds. The method sets a rate of extension of 100 mm/min for Option B — the 50 mm strip, run on a 200 mm gauge — and 300 mm/min for Option A's 25 mm strip on a 75 mm gauge, each held to ±10 %, with jaw separation settable to either gauge within ±1 mm. Most nonwovens break between a few newtons and a few hundred, so the load cell is chosen for that range rather than for the frame. Grips must hold the full strip width at a pressure that does not cut a bonded web, since anything the jaw damages is simply lost from the section, and each jaw face is at least 10 mm wider than the strip. Elongation is normally taken from grip separation, which is acceptable on these materials because nonwoven elongations are large enough that take-up is a small proportion of them.

The fixture this method needs

Standard 25 mm

Pneumatic Vice Action Grip

Pneumatic vice action grips clamp the full specimen width at a constant, even pressure — which is what stops one side slipping or tearing before the other.

Specifications

How the test runs

1. 01Choose Option A or Option B, from the specification.
2. 02Cut specimens to that width with a sharp die or template, in both directions.
3. 03Condition them in the standard atmosphere, or prepare wet specimens as specified.
4. 04Fit wide pneumatic grips with faces suited to a bonded web.
5. 05Set the clamping pressure to hold without cutting.
6. 06Mount the specimen square and free of pre-tension.
7. 07Load at 100 mm/min on the 200 mm gauge for Option B, or 300 mm/min on the 75 mm gauge for Option A.
8. 08Record the maximum force and the elongation at break.
9. 09Reject any specimen that broke in or at the jaws.
10. 10Repeat for the machine and cross-machine directions.
11. 11Report the option used alongside every value.

Calculations

What the report has to contain

• Reference to ISO 9073-3 and the edition
• Whether Option A or Option B was used
• Material identification and mass per unit area
• Direction tested
• Conditioning, or the wet preparation applied
• Gauge length and rate of extension
• Maximum force for each specimen
• Elongation at break, and how it was measured
• Mean and variability for each direction
• Number of specimens rejected for jaw breaks

What goes wrong in practice

Reporting a strength without naming the option, which makes it uncomparable. Averaging the machine and cross-machine directions, when a web laid on a moving belt is oriented by the process and the two commonly differ several-fold. Scissor-cut specimens. And testing only conditioned material for a product used wet — wipes, hygiene articles, medical drapes and filters all work saturated, and webs relying on hydrogen bonding lose most of their strength when they are.