Activewear and fleece pilling: tests, grades and fixes

Why do sportswear and fleece pill?

Abrasion pulls fibre ends out of the yarn, the loose ends tangle into small balls, and those balls either break away or stay anchored to the fabric. Which happens depends largely on fibre strength. Cotton pills tend to wear off and leave fuzz, while polyester and polyamide fibres are strong enough to hold pills in place. That is why a spun polyester or polyester-cotton knit can look worn long before it is.

In activewear the damage follows movement. Look at underarms and side panels where the arms swing, the inner thighs and seat of shorts and joggers, cuffs, and anywhere a bag strap, seat belt or hook-and-loop fastener rubs. On brushed fleece the inner face pills as well, because it rubs against the body and the layer underneath.

Which pilling test should a buyer name?

Name one method and keep it for development and bulk, because results from different methods are not interchangeable. ISO 12945-2 rubs a circular specimen in a Lissajous pattern against an abradant, usually the same fabric, under light pressure and assesses it at set rub stages. The pilling box (ISO 12945-1) and the random tumble methods (ISO 12945-3 and ASTM D3512) tumble specimens instead, so the brief names revolutions or tumbling time rather than rubs.

Two scope notes matter for activewear. ASTM D3512 warns that fabrics treated with a silicone resin may not test satisfactorily, because the silicone can transfer to the cork liners, so ask whether your fabric carries a silicone finish. ASTM D4970, the ASTM Martindale method, is described as particularly suitable for woven fabrics and is not suitable for fabrics thicker than 3 mm, which can rule out high-pile fleece.

How is a pilling grade read?

An assessor views the tested specimen beside an untested piece of the same fabric in a viewing cabinet with low-angle light, then grades it from 5 (no change) to 1 (dense fuzzing or severe pilling across the whole surface). Half grades such as 3–4 are normal. ISO 12945-4 sets out this visual assessment for pilling, fuzzing and matting, and a good report says which of the three drove the grade.

Because the grade is a visual judgement, ask for more than one observer, use the same laboratory for development and bulk where you can, request each specimen’s grade as well as the mean, and keep the tested specimens or clear photographs with the report. A grade quoted without its rub stage or revolutions cannot be compared with anything.

What pilling grade should a buyer accept?

The buyer sets the minimum: ISO and ASTM pilling methods describe how to abrade and grade a fabric, not what passes. For knitted apparel, grade 3–4 is a common minimum, with a separate target for brushed or raised surfaces.

Intertek’s published criteria for its voluntary “Durable” High-Performance Mark for activewear garments are one checkable example. They use the ISO 12945-1 pilling box for 10,800 cycles (180 minutes), assessed after 1 and 15 washes, and ask for at least grade 3–4 on smooth surfaces and grade 3 on raised surfaces. Treat a scheme like this as a reference point for your own specification, not as a rule every garment must meet. Then match the graded surfaces to the product.

• Performance tees and long sleeves: grade the face fabric; check side panels and underarms in wear.
• Polos: grade the body fabric and check the collar, which rubs against the neck.
• Shorts and pants: grade the face and wear-test the inner thigh and seat.
• Hoodies and fleece midlayers: grade both faces, with a separate target for the brushed side.

What should the pilling requirement say?

Write it so that two laboratories would run the same test. As a hypothetical example, a complete line might read: “ISO 12945-2:2020, same-fabric abradant, graded at 2,000 rubs after one wash to ISO 6330 procedure 4N with line drying; minimum grade 3–4 on every specimen; specimens cut from the bulk fabric lot.”

• Method and edition, including the abradant where the method allows a choice.
• Rub stage, revolutions or tumbling time at which the grade applies.
• Condition: as received, or after a named number of washes and drying procedure.
• Surface tested: the face, and the brushed side on fleece.
• Minimum grade, and whether it applies to each specimen or to the mean.
• Specimen source: the bulk fabric lot, not a development swatch.
• Laboratory, who pays, and the retest rule after a failure.

How can a factory improve a fabric that fails?

Most fixes sit upstream of sewing, and each costs something in handfeel, price or minimum quantity. Yarn changes usually make the biggest difference: filament instead of spun polyester, a higher twist, or combed or compact-spun cotton with fewer short fibres. A tighter knit holds fibre ends more firmly. Finishing can remove surface fibres by singeing or shearing, or on cotton by enzyme bio-polishing, while heavy brushing works the other way.

Some trade-offs cannot be designed out. Filament polyester resists pilling but is more prone to snagging, which needs its own test, such as the ASTM D3939 mace method. A brushed fleece will fuzz more readily than a smooth face. Run a short wear trial on the approved sample, check the high-friction zones listed above, and record what you saw next to the laboratory grade.

SenLin agrees tests and inspection scope order by order and publishes no in-house pilling results. A costed bill of materials comes with the quotation, so a pilling requirement can be tied to a named fabric before sampling. Build time for any external laboratory test into the plan alongside the published sample times: 3–4 calendar days for standard styles and 3–7 for custom work.