Colloidal silica for wool spinning and anti-pilling

How colloidal silica works on wool

Colloidal silica deposits a very fine layer of SiO₂ particles, 4–15 nm across, on the fibre surface. Three effects follow:

1. Higher fibre-to-fibre friction. The particles roughen the fibre surface at the nanometre scale. Fibres grip each other instead of sliding apart.
2. Better cohesion. The silica acts as a mild binder between fibres in contact, so the sliver, roving and yarn hold together more strongly. The more the fibres are rubbed during processing, the more the cohesion builds up.
3. Even distribution. The particles are well dispersed and stay where they land, so the effect is uniform along the fibre instead of patchy.

Results in the mill

• Fewer yarn breaks in drafting and spinning.
• Less fly and fibre loss in carding and drafting.
• Higher yarn strength from better fibre cohesion.
• Finer counts from shorter fibre. Mills can spin a higher yarn count from a given wool.

How it is added

Colloidal silica is added at about 2–5% together with the wool oil (spinning lubricant) before carding. The right level depends on the fibre, the oil system and the target count.

Anti-pilling

Pills form when loose fibre ends migrate out of the yarn during wear and tangle into balls on the fabric surface. Anything that keeps fibres anchored in the yarn reduces pilling. Raising inter-fibre friction with silica is one established way to do this, and silica is used in wool finishing systems for that reason. In practice the silica is usually one part of a finishing system together with polymer or silicone finishes. We supply the colloidal silica component to finishing-agent formulators and mills, who evaluate the finished fabric with standard pilling tests such as ISO 12945.

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