Intercrystalline swelling

Zeronian, S. H. Intercrystalline swelling of cellulose in Cellulose chemistry and its applications Nevell, T. P. Zeronian, S. H., Eds. John Wiley Sons New York, 1985,... 

Zeronian, S.H., Intercrystalline swelling of cellulose, in Cellulose Chemistry and Its Applications, Nevell, T.P. and Zeronian, S.H., Eds., Ellis Horwood Ltd., Chichester, England and Halsted Press,... 

The increase of the retention volume of benzene on a modified sample with respect to the initial sample, can be associated, similarly to the case of hexane adsorption, with intercrystalline swelling of the organic complex, when the molecules of aromatic hydrocarbons penetrate between the alkyl chains of the modifying cations adsorbed on the external surface of the mineral. 

Grim (1952) distinguished two modes of swelling in clay soils, namely, intercrystalline and Intracrystalline swelling. Intercrystalline swelling takes place when the uptake of moisture is restricted to the external crystal surfaces and the void spaces between the crystals. Intracrystalline swelling, on the other hand, is characteristic of the smectite family of clay... 

As water swells cellulose in an intercrystalline way (i.e. only within the non-crystalline amorphous regions), a relationship would be expected between accessibility and moisture uptake, and this is indeed found (Figure 5.5). Refining causes cellulosic fibres to swell and it would therefore be expected to cause a change in the water adsorption isotherm. This is indeed observed (Figure 5.6). 

Because cellulose consists of regions of high and relatively low crystallinity, processes to disrupt cellulose operate at two levels intercrystalline and intracrystalline. The conditions required to swell intercrystalline regions are relatively mild, whereas drastic processes are required to affect the high-crystalline regions. These two areas overlap strongly but need to be distinguished. 

Cellulose is hydrophilic and swells in the presence of water. Normally cellulose-water interactions are considered to occur either in intercrystalline regions or on the surfaces of the crystallites and the gross structures. 

Dilute alkali penetrates only accessible regions of the fiber causing intercrystalline or interfibrillar swelling. The latter is much more profound in that it brings about changes in crystal structure of the fibers, as evidenced by mercerization (in the case of alkali) and the formation of ammonia cellulose (in the case of liquid ammonia). 

Intercrystalline corrosion is accompanied by a modification of the structure of the barrier layer that tends to crystallise. This form of corrosion leads to exposure of grains and swelling of the metal. Pitting corrosion is also observed. Above 250 a sharp increase in corrosion is found the kinetics changes to a linear law (Figure D. 1.13). A rapid destruction of the metal is observed. 

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