**3. Activation treatments of cellulose**

Activation methods (Table 3) in general are those that only open and widen existing capillaries, voids and interstices, those that are capable of splitting up fibrillar aggregations, *and* those that are able to disrupt crystalline order and/or change the crystal modification in order to increase accessibility and reactivity of fibrous cellulose substrates, *e.g.* fibres or fabrics.(Krässig, 1993b)


Table 3. Treatments which have an activating effect onto cellulose fibrous substrates.

*Degradation* treatment of cellulose substrate can be performed with numerous chemical reaction routs, which of major significance is hydrolysis and oxidation, or with applying different source of energy such as *UV*/*VIS*, *γ*-irradiation or thermal treatment. *Mechanical* treatment is commonly employed by grinding, milling, beating or cutting to reduce size as well as increase accessible and reactive internal surface of cellulose with varying of activating time and/or temperature.

Activation of cellulose substrates also occurs in water-free organic environments followed by solvent exchange or by inclusion in a subsequently performed reaction. The *solvent exchange* treatment represents the action from water-swollen state with introduction of media which are unable to swell cellulose itself (inert to cellulose). Very similar is *inclusion* treatment which maintains the reactive water-swollen state by introducing inner liquids (*e.g.* benzene) applying the solvent exchange. Examples of chemicals used which provide highly swelling systems causing *intra-fibrillar* as well as *intra-crystalline swelling* include inorganic acids, various salt solutions, inorganic and organic bases, amines and amine complexes, and metal hydroxide solutions. In general, these treatments penetrate the fibre substrate through existing capillaries and pores, open already present voids between fibrillar elements, disrupt fibrillar associations, and finally enter the more easily accessible regions interlinking the crystallites forming the elementary fibrils. From there, they are able to penetrate at suitable treatment conditions; concentration and temperature, and to some extent tension during treatment, have to be considered from both ends into the lattice structure of elementary crystallites, which break open inter-molecular hydrogen-bonds and van der Waals

Activation methods (Table 3) in general are those that only open and widen existing capillaries, voids and interstices, those that are capable of splitting up fibrillar aggregations, *and* those that are able to disrupt crystalline order and/or change the crystal modification in order to increase accessibility and reactivity of fibrous cellulose substrates, *e.g.* fibres or

**3. Activation treatments of cellulose** 

Treatment Action

activating time and/or temperature.

Degradation Chemical Hydrolysis-acid or enzymatic Oxidation

Swelling inter- and intra-fibrillar swelling

 Thermal Applied at different temperatures in various media

Mechanical Milling – dry and wet, grinding, beating, cutting

Solvent exchange From water-swollen state introducing inert media

Inclusion As solvent exchange but introducing inert liquids

*Degradation* treatment of cellulose substrate can be performed with numerous chemical reaction routs, which of major significance is hydrolysis and oxidation, or with applying different source of energy such as *UV*/*VIS*, *γ*-irradiation or thermal treatment. *Mechanical* treatment is commonly employed by grinding, milling, beating or cutting to reduce size as well as increase accessible and reactive internal surface of cellulose with varying of

Activation of cellulose substrates also occurs in water-free organic environments followed by solvent exchange or by inclusion in a subsequently performed reaction. The *solvent exchange* treatment represents the action from water-swollen state with introduction of media which are unable to swell cellulose itself (inert to cellulose). Very similar is *inclusion* treatment which maintains the reactive water-swollen state by introducing inner liquids (*e.g.* benzene) applying the solvent exchange. Examples of chemicals used which provide highly swelling systems causing *intra-fibrillar* as well as *intra-crystalline swelling* include inorganic acids, various salt solutions, inorganic and organic bases, amines and amine complexes, and metal hydroxide solutions. In general, these treatments penetrate the fibre substrate through existing capillaries and pores, open already present voids between fibrillar elements, disrupt fibrillar associations, and finally enter the more easily accessible regions interlinking the crystallites forming the elementary fibrils. From there, they are able to penetrate at suitable treatment conditions; concentration and temperature, and to some extent tension during treatment, have to be considered from both ends into the lattice structure of elementary crystallites, which break open inter-molecular hydrogen-bonds and van der Waals

Table 3. Treatments which have an activating effect onto cellulose fibrous substrates.

Radiation Exposure to UV/VIS or high-energy radiation

towards providing reactive water-swollen state

to maintain reactive water-swollen state

Freezing, ultrasonic agitation

swelling agent/solvent

fabrics.(Krässig, 1993b)

interactions between lattice layers, leading to a widening of lattice distances or even changes in the crystal lattice.(Krässig, 1993b)
