Cotton Mercerised

Recipe pH Pad liquor stability (min) Bleached cotton Mercerised cotton... 

Table 10.31 Comparison of hot mercerising with conventional cold mercerising of cotton [274,277]...

Table 10.32 Comparison of cold and hot mercerising processes for bleached and unbleached cotton and for modal fibres [275,277] ...

One of the earliest fibre pretreatments for improving the dyeability of cotton is of course mercerisation (section 10.5.4). However, more recent research interest in this area has been generated by environmental concerns about reactive dyeing, aiming to enhance substantivity for the modified fibre so that higher absorption and fixation are obtained. This results in less dye (hydrolysed or still active) in the effluent. A further objective is to minimise the usage of electrolyte in the application process. This area has been thoroughly reviewed [392,393]. 

The paramount importance of efficient preparation in producing goods of thorough and uniform absorbency for continuous dyeing cannot be over-emphasised [157,158] all continuous dyeing systems are heavily dependent on this prerequisite. Typical build-up curves on mercerised and unmercerised cotton fabrics in Figure 12.20 illustrate the... 

Figure 12.20 Typical dye build-up curves for pad-steam process variants A and B on mercerised and unmercerised cotton [158]...

Washing Exhaust dyeing of Cl Reactive Red 123 on bleached cotton Continuous dyeing of Cl Reactive Blue 104 on mercerised cotton ... 

Higher substantivity for cellulose. Dye at 45-50 °C with more caustic soda and less salt (none for mercerised cotton or regenerated cellulosic fibres). 

Further, somewhat different characters may be observed according to the process used and especially according to the degree to which the merceri-sation has been carried, intermediate stages existing between the typical forms of mercerised cotton and those of ordinary cotton. 

Unstretched mercerised cotton is less characteristic and resembles more closely the original fibres. The surface is rough, with moderately frequent... 

Stripping test for acid colours. Some direct or " salt dyestuffs are partly decolorised by dilute ammonia and hence might be regarded as add colouring matters. To avoid this error it is useful to add, when this test is made, a piece of mercerised white cotton. With an add dye, the cotton remains white, or is scarcely coloured, and then becomes white again when boiled a second time with dilute ammonia. 

Test for salt colouring matters. A piece of the fabric is boiled in the soap or sodium carbonate solution in presence of white mercerised cotton to see if the cotton remains coloured. 

Decolonsed and colour not restored by air Or persulphate Amo Class or Alizarine on Iron (decolonsed slowly). Boil with soap solution and white mercerised cotton. 

It is worth noting that the mercerisation process, bom in the 19th century, produces a cellulose II structure too, but without dissolution of the fibres and therefore with no reshaping. Cotton fibres are soaked in a concentrated (19%) NaOH solution then washed. Mercerised cotton shows a softer touch and more brilliance than natural cotton. 

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... 

Inks were prepared by mixing microcapsules and binder at 2000 min for 10 min in a 1 1 mass ratio. The fabrics used were 100% cotton ( raw and mercerised) and polyester. 

Figure 2.20 Reflectance spectra and L, a, b diagrams, (a) Raw cotton (b) mercerised cotton (c) polyester.

The rayon samples indicated I and II differ from each other by the degree of their orientation II being better orientated than I). Mercerised native fibres (fibres previously treated with sodium hydroxide) take an intermediate position between native cotton and regenerated fibres so does woodpulp (not included in the table). 

Patel, S. K., Varghese, J. (1983), Reparatory treatments and their influence on dyeing of cotton - a review. Part II Mercerisation and liquid ammonia treatment, Colourage, 30(5), 3-12. 

Plain-weave 100 % cotton woven fabric with a mass of 164 g/m was used in the experiments. In a pre-treatment process the fabric was bleached in an H2O2 bath, mercerised in a NaOH solution and neutralised in a diluted CH3COOH solution. 

The effects of dyeing on the porosity of samples of charcoal cloth and cotton fabric have been examined from nitrogen adsorption isotherms. So too has the effect on the cotton fabric of mercerisation, a treatment which causes dimensional changes to the constituent fibres. On application from 1% sodium chloride solution, increased contents of dye in the charcoal cloth progressively block the micropores and reduce mesopore area but treatment with sodium chloride solution alone increases microporosity. Mercerlsation of the cotton fabric enhances the mesoporous nature of the surface. The effect on porosity of treatment with a reactive dye is less clear-cut it is tentatively suggested that application of the dye narrows the mesopores. 

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