Surfactants in textile, paper and leather industries

In recent time, main attention was focused on the treatment of fiber surfaces, wetting control, and the penetration rate of fabrics by corresponding process solutions. According to [169], the imbibition of fabrics takes place as result of two processes a) a bulk imbibition, since the strands of yarn behave as an assembly of capillaries b) a surface rise due to the formation of surfactant adsorption layers. 

Wetting and wicking are discussed in [16] more in detail. Wetting is the displacement of a fibre-air interface by a fibre-liquid interface which is influenced by surfactants solely. Wicking is the flow of a liquid, driven by capillary forces. The wicking process can proceed in 4 variants 1) capillary penetration only (usually in the absence of surfactants) 2) capillary penetration with simultaneous diffusion of the liquid into the interior of the fibres 3) adsorption of surfactant on the fibres with simultaneous capillary penetration 4) adsorption of surfactant on the fibres with simultaneous imbibition and capillary penetration. In all cases, the effect of penetration increases in the presence of surfactants. 

The so-called synthetic fibres, e.g. nylon, show their peculiarities of wetting in the presence of surfactants of various nature. Capillary wetting rates of nylon fibrous assemblies were studied in [172] using conductivity measurements as well as contact angle measurements by the Wilhelmy method. For sodium dodecyl sulphate and dodecyl trimethyl ammonium chloride a minimum wetting rate was observed near pH 4, which coincided with the isoelectric point of the nylon fibre. When the surface charge increased, the wetting rate increased. 

The wettability of various wood fibres was studied in [173], including bleached and unbleached, and alkyl ketene dimer sized and non-sized fibres. An improvement of the wettability with an increase of the surfactant concentration, except nonionics, was observed for all types of fibres. It has been noted in [174] that the electrokinetic potential of fibres determines considerably the efficiency of their washing and dying. Alkali mercerisation of cotton influences not only the fine structure, morphology and conformation of cellulose molecules, but also the negative electrokinetic potential of the cotton fibres. Based on this, the selection of mercerisation conditions due to changes in the NaOH concentration will allow to 

For the synthetic fibre poly(ethylene terephthalate) it is very important to impart antistatic properties to it [175]. Studies on the effect of the structure of cationic surfactants on the half-life time of static charge decay and surface resistivity (Rs) of PET fibres show best results with a methylated quarternary ammonium salt of a stearyl amine-ethylene oxide adduct or hydrochloride of a lauryl amine-EO adduct with 10 EO. 

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