Testing
Test methods for nonwoven: tensile, absorbency, abrasion
A number without a method is a rumour. The same fabric can pass and fail the same nominal property depending on specimen width, clamp speed and conditioning. This guide explains what each common test measures and how to write the criterion so it survives a dispute.
At a glance
Specification at a glance
| Property | Common method | Specimen and conditions | What it tells you |
|---|---|---|---|
| Tensile strength | Strip test, constant rate of extension | 50 mm strip, 100 or 300 mm/min | Load at break, machine and cross direction |
| Elongation | Same test as tensile | Same specimen | How far the web stretches before break |
| Tear resistance | Trapezoid or tongue tear | Notched specimen | Resistance to tearing from a nick |
| Basis weight | Cut and weigh | Known area, conditioned | Actual gsm and variation across the roll |
| Absorbency rate | Strike through, drop test | Defined volume, defined surface | How fast fluid enters the web |
| Absorbent capacity | Dip and drain | Immersion time, drain time | Volume held per gram |
| Hydrostatic head | Water column | Rising column, defined area | Barrier pressure before leakage |
| Abrasion | Martindale or Taber | Cycles to visible damage | Surface durability and linting potential |
Why conditioning changes the result
Nonwoven absorbs moisture from the air. A web tested in a humid room is softer, stretches further and breaks at a lower load than the same web tested dry. Standard conditioning exists for this reason, and a buyer who tests on arrival without it will see numbers that look like a supplier failure.
Agree the conditioning conditions with the acceptance criterion, and test a control sample you already trust alongside the new batch.
Tensile: machine direction versus cross direction
Almost every web is anisotropic. A parallel laid spunlace might be twice as strong along the machine as across it. If the criterion says only tensile strength, the supplier can pass it with the strong direction, and the buyer can fail the same roll on the weak one.
Write both directions, or write the ratio. The ratio is often the more useful number because it predicts how the web will track and tear on a converting line.
Absorbency: three different questions
How fast, how much, and how much stays in. Strike through answers speed, dip and drain answers capacity, and retention under pressure answers what the end user experiences. A wipe can be fast and hold little, or slow and hold a lot, and both describe a real product.
Abrasion and lint are not the same test
Abrasion measures surface wear under cycles; lint measures what comes off. A fabric can resist abrasion and still shed fibre, which is why wipes buyers test lint separately on the finished article. If lint matters, name the method and the limit, not the word.
Writing an acceptance criterion that survives
A usable criterion has five parts: the property, the method, the specimen, the condition and the limit. For example, tensile strength by strip test on a 50 mm specimen at 300 mm per minute, conditioned at 20 degrees and 65 percent relative humidity, minimum 30 N per 5 cm in machine direction and 15 N per 5 cm across.
Written that way, two laboratories can agree, and a disagreement becomes a measurement question rather than a commercial argument.
Reference samples and drift
Keep a retained sample from each approved batch. When a new batch tests differently, the reference sample tells you whether the method changed or the fabric did. Without one, every dispute starts from zero.
Tell us the application and the acceptance test
The reply names a grade we can run, the tolerance we can hold and a lead time, or says plainly that we cannot make it.
Questions
Common questions
Which tensile standard should we cite?
Cite the method your own laboratory or your customer uses, and add the specimen width and clamp speed. Without those, two laboratories can legitimately report different numbers for the same roll.
Do you test every batch?
Every roll is measured for weight on line; laboratory testing is per batch against the agreed methods. A per roll test is possible if the order calls for it, at a cost.
Can you test to our method if it is not a standard?
Yes, once the method is written down and the equipment exists. An in house method is acceptable as long as both sides test the same way and keep a reference sample.