Cellulose swelling

Hysteresis is observed not only in the sorption isotherms but also in calorimetric measurements of heat of wetting at different moisture contents, and it is thus a combined entropy and enthalpy phenomenon. A reliable explanation for this effect is not currently available, but there is speculation that it is due to the stresses which are induced as the cellulose swells. Since the swelling of cellulose is not completely reversible, mechanical recovery is incomplete and hysteresis will therefore be present both in the internal stress-strain curve of the sample, and also in the water adsorption isotherm. 

The advantage of dehydrating nitrocellulose with alcohol lies in the fact that any residual alcohol may be subsequently included in the solvent. The amount of residual alcohol in nitrocellulose depends not only upon the pressure applied in the dehydration press, but also on the type of nitrocellulose, i.e. it is somewhat larger in more highly nitrated nitrocellulose. Nitrocellulose made from wood cellulose swells in alcohol more readily than that made from cotton which is why the former retains more alcohol and more water. 

Andress and Rheinhardt [9] have discovered that cellulose swells in an aqueous solution of perchloric acid to produce the compound 2C6H10O5-. HC104 which also gives a characteristic X-ray diagram. Miles [8] has suggested that the composition of this substance is ... 

A fundamental difference between starch and cellulose is shown by their behaviour in the presence of nitric acid. Starch brought into contact with nitric acid of over 76% concentration swells and eventually dissolves, whereas cellulose swells only insignificantly and generally does not dissolve (as described already it can only be dissolved in nitric acid of ca. 80% HN03). 

Cellulose swells in electrolyte solutions because of the penetration of hydrated ions which require more space than the water molecules. 

At equilibrium and at a particular RVP, the amount of adsorbed water held by a cellulose generally will be greater if it has been obtained following desorption from a higher RVP and not by adsorption from a lower RVP. The cause of this hysteresis is not fully established [303]. One explanation is based on the internal forces generated when dry cellulose swells, limiting the amount of moisture adsorbed whereas when swollen cellulose shrinks, stress relaxation occurs since the cellulose is plastic and permits a higher uptake of moisture. 

The influence of more than 100 organic media (solvents for the monomer) on radiation grafting of 2,4-dimethyl- and 2-methyI-5-vinylpyridine to cellulose (filter paper of various brands and degrees of grinding) was shown to be associated with two factors, namely cellulose swelling and specific interaction of the organic liquid with the monomer and with cellulose75,76 ... 

L. C. Fidale, N. Ruiz, Th. Heinze, and O. A. El Seoud, Cellulose swelling by aprotic and protic sovlents What are the similarities and differences , Macro-mol Chem. Phys., 209 (2008) 1240-1254. 

Cotton and rayon are dyed readily with dyes that are soluble in the aqueous dye-bath such as the class of direct dyes. The apparent reason for the success of water-soluble dyes with cotton or rayon is that cellulose swells appreciably in the aqueous dye-bath, thereby enhancing diffusion of the large dye molecules into the interior of the fibers. Cellulose exhausts the dye from the bath rapidly, resulting in deep eolor shades for cotton and rayon. For the most part, the classes of soluble dyes are not applicable to the more hydrophobic cellulose acetate and triacetate fibers and fabrics [37,71]. 

The problem of amino acid separation was the starting point for the development of PC. Separation was considered first to be based on partition of the substances between water, bound to cellulose by imbition causing swelling, and a mobile phase, immiscible with water (e. g., phenol saturated with water). This attitude has changed somewhat since it was found that single-phase solvents could also be used with these, the less mobile liquid involved in the cellulose swelling can be regarded as a type of phase, separate from the more mobile solvent-hquid. A partial transition to Freundhch adsorption on the cellulose surface may even occur sometimes. 

C6Hio05)n+ nNaOH (CeHg040Na)n + nH20 Sodium cellulose, swelled cellulose (C6Hg040Na)n + nCS2 n (SC-0CeHg04)n Sodium cellulose xanthate... 

---