Surface-active compounds cellulose

Cellulose acetate yarn, when it appeared on the market in 1921, presented a new problem because it had no adequate affinity for any of the existing dyestuffs. The first satisfactory method of coloration was due to Holland Ellis who observed that many simple insoluble azo dyes would be absorbed by cellulose acetate from an aqueous dispersion, stabilized with sulphated fatty alcohols or similar surface active compounds. A large number of dyes whose application depends on this principle have now made their appearance and are known as the disperse dyes. The demand for this group has increased very significantly with the advent of the truly synthetic man-made fibres. 

M ht scouring operations in which these surface-active compounds are commonly used varv according to the nature of the fibre and the amount and composition of the impurities to be removed. In the case of cotton the cellulose of w hich it is composed is stable to dilute solutions of alkali at the boil. I he imphrities which must be removed are natural oils and waxes, proteins, pectic substances, natural colouring matter, and adventitious dirt. The basic principle of cotton scouring is to boil the goods for several hours at atmospheric, or under elevated, pressure with a 2 per cent solution of sodium h) droxide. 

Surface-active compounds can be produced from all wood constituents. For instance, water-soluble cellulose derivatives and lignin, in the form of lignosulfonates, can be used as dispersing agents in many applications. This chapter focuses on the production of resin and fatty acids as well as sterols and sterol ethoxylates as forest-industry by-products, and their use as surface-active components. Moreover, the potential production of hemi-celluloses and their possible utilization as steric stabilizers of oil-in-water emulsions is also outlined. 

Selective enhancement of room temperatures phosphorescence is achieved by cyclodextrin treated cellulose s ubs t r a t e s, surface active agents3 . and for heterocyclic compounds by absorption on silica gel coated plates submerged in chloroform-containing solvent s3. ... 

Surface Activation. Acid Activation. Acid treatment of cellulose and hemicelluloses generally leads to hydrolysis to monosaccharides, which can subsequently dehydrate and condense to form furan-type compounds such as furfural and its 5-hydroxymethyl adduct. Further reactions lead to polymeric materials of dark color as well as to monomers such as levulinic acid, formic acid, and angelica lactones. Various condensation and solvolysis reactions also accompany the acid treatment of lignin 123). The hydrolysis, dehydration, and condensation reactions have been used to explain formation of covalent bonds between surfaces (85), increase in water resistance (85, 124), and weakening of wood (75) in nonconventional plywood or particle board production. However, very little factual information is available on how far, in terms of the consecutive reactions mentioned, and in what direction, in terms of the parallel reactions mentioned, does the surface of lignocellulosic materials actually change... 

In soils and clays the most generally present biopolymers that naturally occur in the adsorbed state on mineral and clay particles are humic substances , or humic acids these are decomposition products of lignin, whidi is the major non-cellulosic polymer in wood and other plant debris. Humic acids (also called allomelanins (Merck Index, 1989)) are for the greater part polyphenolic compounds, usueJly anionic polyelectrolytes, which can complex metal ions, and are surface active and thus capable, upon adsorption onto mineral particles, to enhance their suspension stability in aqueous media (Chheda and Grasso, 1994). 

The complex three-dimensional structure of these materials is determined by their carbon-based polymers (such as cellulose and lignin), and it is this backbone that gives the final carbon structure after thermal degradation. These materials, therefore, produce a very porous high-surface-area carbon solid. In addition, the carbon has to be activated so that it will interact with and physisorb (i.e., adsorb physically, without forming a chemical bond) a wide range of compounds. This activation process involves controlled oxidation of the surface to produce polar sites. 

This includes reactions of the polymer groups with metallic sites on the particle surface that may result in the formation of stable or insoluble compounds through covalent, ionic or coordination bonding. Carboxyl flocculants such as polyacrylic acid and carboxyl-methyl cellulose can chemisorb on the surface of calcite and sphalerite which have calcium or zinc sites on them. Certain flocculants, such as cellulose and starch with xanthate and polyacrylamide with dithiocarbamate with high chemically active groups, have been found to exhibit selective reaction with sulfide minerals. Such complexing polymers have been investigated for their use in selective flocculation processes. 

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