Mercerization temperature

It is interesting to note that all the new aromatic systems, as described, undergo displacement polymerizations in DMAC solvent by the K2CO3 method, except perfluoroalkylene [10] and amide activated polymerization [9], which were performed in NMP solvent. The displacement polymerization in DMAC solvent was carried out at 155-164°C. poly(aryl ether ketones) require less reaction time (3-6 h) than other aromatic systems for synthesis of polyethers [15]. Synthesis of the fluorinated polyether as reported by Irvin et al. [16] was carried out at room temperature for 16 h (Mw = 75,000), whereas the same polymer by Mercer et al. [17] was synthesized at 120°C for 17 h (Mw = 78,970). 

An older method of cellulose fiber modification is mercerization [22,33-36], which has been widely used on cotton textiles. Mercerization is an alkali treatment of cellulose fibers. It depends on the type and concentration of the alkalic solution, its temperature, time of treatment, tension of the material, and the additives used [33,36]. At present there is a tendency to use mercerization for natural fibers as well. Optimal conditions of mercerization ensure the improvement of the tensile properties [33-35,37] and absorption characteristics [33-35], which are important in the composing process. 

Variety Temperature Scouring and bleaching Caustic mercerization Liquid ammonia treatment Removal techniques... 

These techniques have been used to elucidate the effects of variety [289], temperature [287], scouring-bleaching [290], caustic mercerization [290-292], liquid ammonia treatment [290,292,293], cross-linking with different agents under varying conditions [294-298], dye-ability [296,299], and treatment with cellulases [300-302], on the cotton. The trends observed are summarized in Table 5.8. 

Hot mercerization allows better penetration of the alkali into the fibers than the ambient temperatures used normally [312]. However, to obtain optimum improvement in properties the caustic has to be washed out after the fabric is cooled. 

MERCERANT BEA is a non-phenolic, non-staining mercerizing assistant having excellent wetting ability in 18-25% caustic soda at room temperature. 

MERCERANT BEA can also be used as a wetting agent in low strength caustic (e.g. 5%) at elevated temperatures (eq. 180F). Under these conditions 1 g/1 or less gives excellent wetting. 

Strong alkali solutions acting on cellulose (at room temperatures) produce alkali cellulose. The studies on the structure of alkali cellulose [43] obtained with 20-40% NaOH solutions indicated that the substance is not a true alcoholate but an addition complex, RceiiOH NaOH. A true alcoholate can be obtained, for example, from dry cellulose and Na in liquid ammonia. Alkali cellulose has a large range of applications as an intermediate product in the preparation of cellulose ethers, and xanthate (dithiocarbonate), as well as in cellulose mercerization. 

Allison, S.W. Goedeke, S.M. Beshears, D.L. Cates, M.R. Hollerman, W.A. Womack, F.N. Bergeron, N.P. Bencic, T.J. Mercer, C.R. Eldridge, J.I. Advances in high temperature phosphor thermometry for aerospace applications. Proceedings of the 39th AIAA/ASME/SAE/ ASEE Joint Propulsion Conference, 2003 AIAA-2003-4584. 

Lustre also depends on other factors. Mercerization reduces the axial ratio and increase the light scattering within the fibre (transparency) and thus increases the lustre. The presence of short fibre on the surface decreases lustre and is removed during singeing. Lustre increases from 180 g/1 of NaOH solution to a maximum at 260-300 g/1, then decreases slightly [45], Theoretically lustre increases with an increase in swelling and therefore with a decrease in the temperature of merceriza-... 

Cotton can be causticized or half-mercerized to increase the dye uptake and economics up to 25% may be realised. Semi-mercerization or causticization is carried out in caustic soda solution between 25 and 30 Tw at a temperature of 20-25 C, sometimes without stretching the cloth to restore original dimensions. Sodium hydroxide solution above 30 Tw the rate of colour absorption decreases. Semi-mercerization is also an important step where heavy shades are required with the expensive vat colours. Better results are also observed with aniline black on goods which have received a semi-mercerization treatment. 

The reactivity of mercerized cotton is increased by about 1 / times at lower temperature in comparison to that of unmercerized cotton. The increased reactivity is not so marked when mercerization is carried out under tension. The reactivity ratio is generally referred to as the ratio of copper number of the mercerized to unmercerized samples. The increased reactivity increases dye absorption, moisture sorption and chemical reaction, but at the same time it also accelerates the reaction with acids and oxidising agents and is susceptible to degradation. 

Mercerization improves dimensional stability of cotton woven fabrics [63]. When knitted fabrics are compared with respect to their relative openness, temperature increases can be said to improve mercerization because when the goods are bleached and then mercerized, the fabric becomes more dense. However, when unbleached fabrics are mercerized, the fabrics become more open [64]. Mercerization also gives moderate improvement in crease recovery of cotton fabrics [65] as well as some protection against the decrease in tensile strength caused by easy-care finishing. 

In hot mercerization fabric is either padded through hot caustic solution or at ambient temperature and then passed through steamer where the fabric is steamed. The process sequence of two step hot mercerization is as follows ... 

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