Surface Modification of Cellulose Acetate with Cutinase and ...

Subchapter 3.1
3.6. Felting and shrinkage
One of the intrinsic properties of wool is its tendency to felting and shrinkage under a
moisturizing environment, heat or mechanical agitation. Wool shrinkage is basically
due to its scaly structure.
The shrinkage behaviour of wool can be regulated to a greater or smaller degree by
various chemical means. There are various successful commercial shrink-resist
processes available for textile industries that have been developed decades ago. These
shrinkproofing processes aim at the modification of the fibre surface either by oxidative
or reductive methods and/or by the application of a polymer resin onto the surface.
These processes can be combined in 3 groups:
Subtractive processes – The first type of shrinkproofing treatment involves chemical
attack on the cuticle of the fibres using a chlorine agent. Chlorination was introduced as
a shrinkproofing treatment during the latter half of the nineteenth century (Makinson,
1979). The principal mode of action of subtractive antifelting treatment is that it making
the cuticle cells softer in water than those of untreated fibres. This softening is the result
of oxidation and scission of the numerous disulfide bonds in the exocuticle of the fibre
and causes a reduction in the directional frictional effect (Makinson, 1979).
Additive processes – The second class of shrinkproofing treatments consists on the
addition of a polymer to the wool. This treatment promotes fibres to stick among
themselves at many points along their length, thereby preventing relative movement and
thus shrinkage. The polymer can be applied to wool fabric or yarn as solutions or
emulsions. The polymers contain reactive side-chains, which form cross-links between
the polymer chains during a curing process and may form covalent links with the wool
protein.
Combination of subtractive and additive processes- The most common surface specific
treatment for wool is probably the chlorine-Hercosett process which renders the wool
fibre shrink-resistant. The process uses chlorine gas generated in situ from sodium
hypochlorite and sulphuric acid or chlorine gas dissolved in water. The treatment is
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