Why do cotton/polyester T-shirts pill?

Short answer: All fabrics form fuzz when fibres work loose from the surface during wear and washing. In cotton the loose fibres are relatively weak, so pills often break off. Polyester fibres are much stronger, so the fibre ends tangle into pills and stay anchored to the fabric, making pilling more visible on blends. Short fibres, low yarn twist, open-end spinning, loose knits and abrasion at the sides and underarms make it worse. Ways to reduce it include using a low-pill polyester fibre, more twist or compact spinning, a tighter knit, singeing or anti-pilling finishes, and reviewing the blend ratio. Test pilling with ISO 12945-2 after washing and set a minimum grade in the specification.

Why blends pill more visibly

• Strong polyester fibres anchor pills so they do not fall off.
• Cotton fibres can break and wrap around polyester ends.
• Abrasion at the sides, underarms and where bags rub concentrates pilling.

What reduces pilling

• Low-pill or modified polyester fibre.
• Longer-staple fibres and combed or compact yarns.
• Higher yarn twist and tighter knit, balanced against softness.
• Singeing, shearing or anti-pilling finishes.
• Washing inside out on a gentle cycle.

Testing

• Use ISO 12945-2, the modified Martindale method, on washed fabric.
• Wash specimens first with an ISO 6330 procedure when washing affects the result.
• Compare grades with the approved standard and the specification.

A worked example

The brand tests its 60/40 fabric and a new option using low-pill polyester and compact cotton yarn. After washing, the original fabric grades around 2 to 3 while the new option grades around 4 at the same number of rubs. The new fabric costs a little more, but the brand adopts it and adds a minimum pilling grade to its specification.

Care advice for customers

Washing inside out, using a gentle cycle, avoiding overloading the machine and not washing tees with rough items such as jeans or towels all reduce surface abrasion. Lower tumble drying heat and shorter cycles also help. These tips can go on a hang tag or product page, but they do not replace choosing a fabric that resists pilling.

Limits

Pilling grades are subjective and test conditions affect results. A lab result does not fully reproduce how each customer wears and washes the shirt.

Facts, recommendations and uncertainty

Established: polyester blends hold pills because the stronger fibres anchor them. Recommendation: choose low-pill fibres and tighter yarns, test with ISO 12945-2, and set a minimum grade. Uncertain: the exact grade needed for your customers' wear patterns.

Sources and further reading

• ISO 12945-2:2020 — Pilling, fuzzing or matting, modified Martindale method
• ISO 6330:2021 — Domestic washing and drying procedures for textile testing

Standards and regulations are referenced by their published scope. Test parameters, cycles and pass levels should be agreed with your laboratory for the specific product; legal requirements should be confirmed for each destination market.