Thursday, 28 May 2015

Wool, too tight for comfort?

Wool has been a precious raw material for people for a long time. Yarns have been spun out of wool fibres for several millenniums. As the range of available fibres was limited in the past, wool used to be a very valuable commodity. Today we are able to select between
a huge variety of fibres with varying properties, but nevertheless, the percentage of wool in fibre production all over the world averages out to a few percent.

The continuing use of wool – in spite of the competition with other natural fibres and new synthetic fibres – for suits, coats and pullovers can be attributed to the unique properties of wool:
- thermal regulative due to high amounts of air embedded in the fibre
- high absorption of moisture
- low tendency to creasing
- low flammability

However, wool has not just got properties which offer high wearing comfort. A big disadvantage, which emerges during washing, is the felting tendency. Under the influence of warm, alkaline water, the scales surrounding the wool fibres rise. If the wool fibres are additionally moved, the fibres wedge with each other more and more since they can only glide in one direction due to the scales. The fabric shrinks and gets tighter.

To prevent felting of wool and to make wool washable in normal household washing machines, several methods have been developed:
- softening/removing of scales by chemical modifications (oxidation)
- covering of scales by application of a resin
- combination of oxidation and enzymes
- plasma treatment
- combination of removal and covering (so called Chlor-Hercosett-process)
- Petry-anazym-proces

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