Solutions of cellulose

Carbon disulphide is an excellent solvent for fats, oils, rubber, sulphur, bromine and iodine, and is used industrially as a solvent for extraction. It is also used in the production of viscose silk, when added to wood cellulose impregnated with sodium hydroxide solution, a viscous solution of cellulose xanthate is formed, and this can be extruded through a fine nozzle into acid, which decomposes the xanthate to give a glossy thread of cellulose. 

Filtration of viscose is not a straightforward chemical engineering process. The solution of cellulose xanthate contains some easy-to-deal-with undissolved pulp fibers, but also some gel-like material which is retarded rather than removed by the filters. The viscose is unstable and tends to form more gel as it ages. Its flow characteristics make the material close to the walls of any vessel or pipe move more slowly, get older, and gel more than the mainstream viscose. So while filtration can hold back gels arising from incomplete mixing, new gels can form in the pipework after the filters. 

The imminium chloride formed was transformed, in-situ, into the corresponding carboxyhc acid derivative, this was added to a solution of cellulose in LiCl/DMAc. Palmitic, stearic, adamantane-1-carboxylic, and 4-nitrobenzoic acids were employed. The DS of the corresponding esters increased as a function of increasing the ratio oxalyl chloride/AGU. The solubihty of the products obtained in aprotic solvents was tested GPC results have indicated negligible degradation of the polymer [200]. 

I) cellulose nitrate to which the Explosives Act 1875 applies or (ii) solutions of cellulose nitrate where the nitrogen content of the cellulose nitrate 12.3 /n by weight and the solution contains 55 parts of cellulose nitrate per 100 parts by weight of solution. 

Front-silvered mirrors can be pohshed with optical rouge on a pad of chamois leather over cotton wool. Care is necessary because it is easy to polish completely through the silver. Back-silvered mirrors can be protected by first varnishing the silver and then painting the varnish. Front-silvered mirrors can be protected with a thin coat of lacquer, such as a dilute solution of cellulose nitrate in amyl acetate. The lacquer should not be too thin, or interference colours may be produced. 

Peguy, A. el al., J. Appl. Poly, Science, 1990, 40(3/4), 429 Solutions of cellulose in wet methylmorpholine oxide can undergo exothermic reaction to the point of explosion if confined at elevated temperatures from about 120°C or if otherwise heated to 180°C. The reaction is catalysed by some metals, notably copper. 

This term was originally intended to denote all kinds of man-made textile fibres, but is now applied only to cellulose types. Viscose rayon (regenerated from a solution of cellulose xanthate in sodium hydroxide) accounts for the greater part of world rayon production. Acetate rayon and cuprammonium rayon are relatively unimportant. 

That type of rayon which is regenerated from viscose, a syrupy liquid consisting mainly of a solution of cellulose xanthate in dilute sodium hydroxide. 

In 1857, Schweizer discovered that ammoniacal solutions of copper hydroxide could dissolve cellulose. Cellulose is a versatile polymer which is found in plenty in nature in the form of cotton, hemp, jute, flax, etc. In 1891, first attempts were made to spin a solution of cellulose. The cellulose produced like this is known as Bemberg Rayon and is still being produced commercially in Germany, Italy, Japan and USA. 

An example is provided by the work of Valtasaari39 on solutions of cellulose in the coloured complex solvent FeTNa, which necessitates this correction even though the transmittance maximum of this solvent lies conveniently at X0 = 546 nm. In the absence of an absorption correction the molecular weight obtained will be lower than its true value. 

Preparative GPC of Cellulose Triacetate Sample. A 1% (m/V) solution of cellulose triacetate (medium) prefiltered through porosity 3 glass sinter was fractionated by repeated injection through the column set described above. Seven cuts covering the entire elution curve were collected. The flow rate, injection time and the experimental conditions were identical to those stated above. 

Bianchi et al. (19) spun fibers from isotropic and anisotropic solutions of cellulose (D.P. 290) in LiCl (7.8%)-DMAC solutions. The fiber mechanical properties increased throimh the isotropic-anisotropic transition with elastic moduli as high as 22 GPa (161 g/d) being obtained. 

Solutions of cellulose in NH3/NH4SCN (27 73 w/w) are liquid crystalline at concentrations from 10-16% (w/w) depending on the cellulose molecular weight (64). Optical rotations of the solutions indicate the mesophase is cholesteric with a left-handed twist. The solvent does not react with cellulose. Recently, Yang (60) foimd that cellulose (D.P. 210) formed a mesophase at 3.5% (w/w) concentration at a NH3/NH4SCN of 30 70 (w/w). 

Yang et al. (15) spun fibers from a partially (biphasic) nematic solution of cellulose in 1 3/NH4SCN. Tenacities of ca. 3 g/d and moduli of ca. 155 g/d were obtained. 

Bheda et al. ( ) showed that cellulose triacetate forms a mesophase in dichloroacetic acid. Navard and Haudin (18) examined the thermal behavior of liquid crystalline solutions of CTA in TFA. Navard et al. (23) studied the isotropic to anisotropic transitions of solutions of cellulose triacetate in TFA using differential scanning calorimetry. Navard and Haudin (S2) studied the mesophases of cellulose and cellulose triacetate calorimetrically. Navard et al. (83) report similar studies. Meeten and Navard (97) showed the twist of the cholesteric helicoidal structure of CTA and secondary cellulose in TFA is left-handed. 

The Kinetics of Solution of Cellulose Nitrates in Explosive Plasticizers , PATR 1786 (Oct 1950)... 

Cellulose acetate was initially employed as a replacement for the more flammable cellulose nitrate. The degree of acetylation of this ester can be varied the commercial product is 80 to 97% acetylated. Both films and fibers are made by the extrusion of solutions of cellulose acetate. The films and fibers are oriented in the direction of puli, and thus they have preferential strength in that direction. 

The relative viscosity of solutions of cellulose nitrate in acetone was measured and extrapolated to zero rate of shear ... 

Solutions of cellulose, its esters and ethers are colloidal solutions. They are reversible lyophilic colloids. The most important characteristics of such solutions are as follows. 

Formerly it was believed that in their physical properties, as for instance no increase in boiling point and in osmotic pressure, colloidal solutions of cellulose derivatives were radically different from solutions of crystalline substances having small molecules. Now, however it is clear that the difference is not so considerable and that a close analogy exists between solutions of cellulose and its derivatives and those of substances of low molecular weight. 

One of the arguments against the existence of micelles in solutions of cellulose derivatives is the fact that when cellulose is converted into its derivative, e.g. an ester, the degree of polymerization remains almost unchanged. This however only occurs when ester fonnation is carried out under strictly controlled conditions (nitration at low temperature with nitric and phosphoric acids mixture — p. 341, or with nitric, acetic acids and acetic anhydride mixtures — p. 344). The relevent data found by Staudinger and Mohr [32] are collected in Table 40. 

Solutions of cellulose derivatives, such as nitrocellulose, passed through a fine porous filter demonstrate neither the Tyndall effect, nor the presence of particles visible in the ultra-microscope. This is one more piece of evidence that the properties of these solutions are the same as those of substances with low molecular weight. The same holds for cellulose in ammoniacal solutions of cupric oxide ( cupr-ammonium ). 

Thus in the instance of 1% solution exposed for an interval of 4 hr to the action of light the decrease in viscosity is 0.3-0.7%. With 10-20% solutions, on the other hand, the reduction in viscosity during the same period is 25.0-34.2%. Mine s experiments showed that in solutions of low viscosity the reduction of viscosity could remain unobserved. Claesson and Wettermark [92a] investigated the irradiation of solutions of cellulose nitrate with light of wave-length 253 rafi. The depolymerization was followed viscosimetrically and the chain breakage was found to obey the course predicted theoretically for a random process with a quantum yield of 0.01-0.02. 

Fig. 116. Diagram by Trogus [5] /—Formation of the addition (Knecht) compounds, //—Nitrationjof cellulose (in % N), ///—Freezing temperatureof HNO3-H2O solutions, IV— Partial vapour pressure of HNO3 in aqueous nitric acid. Hatched area — strong swelling of cellulose fibre. Cross hatched area — solution of cellulose fibre...

For these measurements, temperature has been varied between 55 and 110° C. In this temperature range, the solvent viscosity changes by a factor three 4.7 to 1.5 cps). It is very improbable that a noticeable internal friction factor would change just by the same factor. Moreover, as has already been pointed out at the end of Section 5.2.2, the curves obtained by plotting cot2 c vs reduced shear stress fjN are practically coinciding for dilute solutions of cellulose tricarbanilate fractions with M S 500,000 and for anionic polystyrenes. So one can conclude that the internal friction of the thermodynamically stiff molecules of cellulose tricarbanilate must be rather low. 

The properties of cellulosic graft copolymers have been studied to a considerable extent but mainly in the form of grafted fibers or films of ill-defined composition. However, a few properties have been measured on well defined grafts (147). It was found that solutions of cellulose acetate-polystyrene grafts in dimethyl formamide are less tolerant to the addition of polystyrene than cellulose acetate itself. This result was attributed to the greater coil expansion in the case of the graft copolymer. On the other hand, the tolerance of the grafts to each homo-... 

Figure 5. Changes in optical rotation on cooling a 1% solution of cellulose sulfate (DS 0.8)...

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