Chlorhexidine (CH) is an effective antimicrobial agent. There has been very little work published concerning the interactions of CH with, and its adsorption mechanism on, cellulose. In this paper, such physical chemistry parameters are examined and related to computational chemistry studies. Adsorption isotherms were constructed following application of CH to cellulose. These were typical of a Langmuir adsorption isotherm, but at higher concentrations displayed good correlation also with a Freundlich isotherm. Sorption was attributed to a combination of electrostatic (major contribution) and hydrogen bonding forces, which endorsed computational chemistry proposals: electrostatic interactions between CH and carboxylic acid groups in the cellulose dominate with a contribution to binding through hydrogen bonding of the biguanide residues and the p-chlorophenol moieties (Yoshida H-bonding) with the cellulose hydroxyl groups. At high CH concentrations, there is evidence of monolayer and bilayer aggregation. Differences in sorption between CH and another antimicrobial agent previously studied, poly(hexamethylenebiguanide) (PHMB), are attributed to higher molecular weight of PHMB and higher charge density of biguanide residues in CH (due to the relative electron withdrawing effect of the p-chlorophenol moiety).

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Metal mordanting, or the application of metal salts, is a common method of improving the light fastness in dyeing with natural colourants. This review presents the results from a survey of the literature on metal mordanting to assess what levels of correlation exist between mordant‐induced effects (changes in colour and colour depth) and the changes in light fastness, what is known about the mechanisms of mordant‐induced improvements of light fastness, and how the salt levels used in coloration processes compare with the limits on metal levels in wastewater and on the dyed substrates. No strong interrelationships are found between the mordant‐induced effects and light fastness improvements. Knowledge about mechanisms of mordant effect on light fastness appears, in large part, to be derived from empirical correlations. However, as light fastness is affected by a multitude of factors, the correlations do not always hold true. It is found that residual metal contents in spent dye/mordanting liquors are generally not reported. However, with rough calculations, it is estimated that, with even the lowest reported salt concentrations, the metal contents in spent liquors exceed environmental release limits. The metal contents on dyed substrates are also not generally reported, but similar estimations show that the contents of heavy metal on dyed substrates (when copper and chromium salts are used as mordants) also exceed limits. On the basis of these observations, the authors make suggestions for elements to be included in investigations on furthering the use of natural colourants in textile dyeing.

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The degrees of salt sorption were determined in lyocell and viscose fibers immersed in aqueous solutions of salt-alkali mixtures with the aim of using salt sorption as an indirect measure of changes to fiber accessibility in presence of alkali. The salt-alkali mixtures used were combinations of NaOH with NaCl or NaBr, and of KOH with KCl or KBr. In general, salt sorption in fibers increased with increase in alkali concentration up to 2 mol/l, and did not change significantly thereafter. The accessibility of Br ) salts was greater than the Cl ) salts, but that of the Na + salts was greater than the K + salts. These trends in salt sorption indicate that salt accessibility in fibers is not influenced by the size of hydrated salt ions, but by the forces of electrostatic attraction and repulsion between the charged fiber surface and salt cations and anions.Nomenclature: [X] f -Alkali or salt sorbed by fiber (mol/g Fiber); [X] s -Alkali or salt content in treatment liquor (mol/l); [Y] f -Alkali or salt desorbed by fiber (mol/g fiber); [Y] s -Alkali or salt content in wash liquor (mol/l); CLY -Lyocell fibers without spin finish; CLY-sp -Lyocell fibers with spin finish CV -Viscose fibers; MC -Fractional moisture content of fibers; SRV -Solution retention value of fiber (ml/g); V -Volume of wash liquor (ml); W C -Weight of conditioned fibers; W D -Weight of dry fibers (g) W S -Weight of oven-dried fibers (g); W W -Weight of wet fibers (g); q -Density of treatment solution (g/ml)

We synthesized cellulose/gypsum composites in the presence and absence of sodium alginate and investigated the interaction between the composite components as well as the mechanical properties of the final composites. Four different types of cellulose fiber materials were used: cellulose UFC100, cellulose B400, nanofibrillated cellulose, and Lyocell fiber. For all investigated composites the total amount of admixed cellulose was between 1 and 2 wt%, the amount of admixed sodium alginate was 0.5 wt%. We determined the morphology of the composites and observed that the particle and fiber dimensions of the admixed cellulose affect the mode of gypsum-gypsum interlocking and the total porosity of the composites. This in turn had a substantial influence on the mechanical properties of the final composite materials. The addition of sodium alginate resulted in an increase of ultimate strain values. Composites with Lyocell fiber, a synthetic fiber, also had a high Young's modulus.

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