5 min read
Reading a nonwoven data sheet
Basis weight, thickness, tensile strength, absorbency, lint — what each line on a nonwoven data sheet actually tells you, and what it leaves out.
A data sheet is a comparison tool, not a brochure. It only works if the numbers on it were produced the same way as the numbers you are comparing them with. Most procurement mistakes in nonwovens come from comparing figures that were measured differently, not from buying the wrong material.
Basis weight is a range, not a point
Basis weight is mass per unit area. It is the first number on any sheet and the one that most affects absorbency and cost. What matters is whether the sheet states a target with a tolerance, or a single figure with no tolerance at all. A target without a tolerance cannot be checked on delivery.
Thickness and bulk are not the same thing
A heavier web is not automatically thicker, and a thicker web is not automatically more absorbent. Embossing raises apparent thickness, perforation removes material, and neither changes basis weight. If a sheet quotes thickness without saying whether the sample was compressed, the figure is not comparable.
Tensile strength needs a direction
Nonwoven webs are anisotropic: strength in the machine direction usually differs from strength across it. A sheet that quotes a single tensile figure is quoting half the story. For a towel that will be wrung or wrapped, the cross-direction figure is often the one that predicts failure.
Absorbency has at least three meanings
How fast liquid is taken up, how much is held, and how much is released under pressure are three different measurements. A towel can be fast and hold little, or slow and hold a great deal. Which one a buyer needs depends on the use: a salon towel has to take water out of hair quickly, a bath towel has to hold enough to dry a body.
If the sheet does not name the method, the number is decoration.
Lint is usually absent, and usually matters
Loose fibre — lint — is what a customer notices on a dark surface or on skin. Not every supplier measures it, and few volunteer it. If the application is facial, ask for the method and the result rather than an assurance.
What a good sheet looks like
A sheet you can act on states the method next to every figure, gives a tolerance for the physical dimensions, and names the construction revision it applies to. Ours also states the date, because a number measured three years ago is a claim about a different material.