Surface Modification of Cellulose Acetate with Cutinase and ...

Chapter 1
Wool fabric has the tendency to felt and shrink on wet processing. The shrinkage
behaviour of wool can be regulated by various chemical means. The most successful
commercial shrink-resistant process available is the chlorine-Hercosett process
developed more than 30 years ago (Heiz, 1981). Although the excellent advantages of
this method (good antifelt effect, low damage and low weight loss), there are some
important drawbacks (limited durability, poor handle, yellowing of fibres, difficulties in
dyeing and environmental impact by the release of absorbable organic halogens to the
effluents) (Julia et al., 2000; Schlink and Greeff, 2001).
Several authors have suggested the use of benign chemical processes such as low
temperature plasma to treat wool (Kan et al., 1998; Kan et al., 1999; Kan et al., 2006a;
El-Zawahry et al., 2006; Kan et al., 2006b). Plasma treatment is a dry process, in which
the treatment of wool fibre is performed by electric gas discharges (plasma). It is
regarded as an environmentally friendly process, as no chemicals are used and can be
applied as an effective technique for modifying the surface properties of wool without
much alteration of the interior part of the fibre. However, costs, compatibility and
capacity are obstacles to commercialization of a plasma treatment process and the
shrink-resist properties obtained do not impart a machine-washable finish, which is one
of the main objectives (McDevitt and Winkler, 2000). The posterior application of a
natural polymer, such as chitosan, was also investigated to improve wool shrinkresistance
or anti-felting properties (Onar and Sariisik, 2004).
More recently, mainly for ecological reasons, proteases, namely subtilisin type, are
being studied as an alternative for chemical pre-treatment of wool. Several studies
reported that pre-treatment of wool fibres with proteases, before the dyeing process, has
been shown to improve anti-shrinkage properties, to remove impurities and to increase
dyeing affinity (Levene et al., 1996; Parvinzadeh, 2007).
However, due to its small size, the enzyme is able to penetrate into the fibre cortex
which causes the destruction of the inner parts of wool structure (Shen et al., 1999).
Several reports show that increasing enzyme molecular weight by chemical crosslinking
with glutaraldehyde or by the attachment of synthetic polymers like polyethylene
glycol, is possible to avoid enzyme penetration and the consequent reduction of strength
and weight loss (Silva et al., 2004; Schroeder et al., 2006). Some of these processes
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