All-cellulose

Ana.eroblc Digestion. Methane can be produced from water slurries of biomass by anaerobic digestion in the presence of mixed populations of anaerobes. This process has been used for many years to stabilize municipal sewage sludges for purposes of disposal. Presuming the biomass is all cellulose, the chemistry can be represented in simplified form as follows ... 

Cellulose Acetate. Almost all cellulose acetate, with the exception of fibrous triacetate, is prepared by a solution process employing sulfuric... 

Solution Process. With the exception of fibrous triacetate, practically all cellulose acetate is manufactured by a solution process using sulfuric acid catalyst with acetic anhydride in an acetic acid solvent. An excellent description of this process is given (85). In the process (Fig. 8), cellulose (ca 400 kg) is treated with ca 1200 kg acetic anhydride in 1600 kg acetic acid solvent and 28—40 kg sulfuric acid (7—10% based on cellulose) as catalyst. During the exothermic reaction, the temperature is controlled at 40—45°C to minimize cellulose degradation. After the reaction solution becomes clear and fiber-free and the desired viscosity has been achieved, sufficient aqueous acetic acid (60—70% acid) is added to destroy the excess anhydride and provide 10—15% free water for hydrolysis. At this point, the sulfuric acid catalyst may be partially neutralized with calcium, magnesium, or sodium salts for better control of product molecular weight. 

Tensile strength of the fibers is also determined by the refinement of the fiber [14] (Fig. 4). Hydrophilic properties are a major problem for all cellulose fibers. The moisture content of the fibers amounts to 10 wt% at standard atmosphere. Their hydrophilic behavior influences the properties of the fiber itself (Table 3) as well as the properties of the composite at production [15]. 

Narrow Molecular Weight Triacetate Fractions. Narrow molecular weight cellulose triacetate fractions were obtained by both fractional precipitation and preparative GPC as described above. The number average molecular weight (1 ) of the various fractions and cuts was determined by high speed membrane osmometry. A linear dependence of GPC elution volume on log molecular weight for all cellulose triacetate fractions was found in both methylpyrroli-done and dichloromethane. 

Pigments. Pigment-printed textiles represent the highest percentage of all printed textiles, accounting for between 40 and 50% of all cellulose and over 90% of polyester-cotton blend prints. 

An important hypothesis formulated by Heuser was an extension of one suggested much earlier by Anselme Payen, but it was based on firmer experimental data. It stated that, irrespective of source, all celluloses, when freed from other components (or impurities), had one and the same constitution. The various chapters in Heuser s Lehrbmh rested on this assumption. 

The DP results rendered by most of these methods are low and inaccurate, especially when the celluloses are alkali-sensitive, i.e., contain carbonyl groups bringing about chain cleavage in alkaline solutions or active carbonyls, which initiate the stepwise depolymerization of the cellulose chains (known as the peeling reaction) according to the carbonyl elimination mechanism of Isbell et al. [416-420]. The most accurate method for DP determination in all celluloses is the nitration method, in which the cellulose is nitrated in a solution of nitric and phosphoric acids and phosphorus pentoxide, and dissolved in butyl acetate [420-422]. 

The solvent compositions chosen for study were in the range of 70 to 80% (w/w) NH4SCN (0.33 to 0.47 mole fraction) reported by Cuculo and Hudson (25) to be good solvents for cellulose. Prior to use, all cellulose samples and the NH4SCN were dried under vacuum for 4 hours at 80 C except where noted. Solvents relatively richer in NH4SCN were prepared by adding NH4SCN to a stock solution. 

Practically all cellulose acetate manufactured at the present time is the acetone-soluble product, ranging from 37% to 41% acetyl content. Cellulose mixed esters now produced in quantity include cellulose acetate propionate of 33% propionyl content, cellulose acetate butyrate of 16% butyryl content, both of which are used largely for protective coatings and films, and cellulose acetate butyrate of 36% butyryl content used for plastics. 

Gellans, guar gum, konjac, glucomannans, larch arablnogalactan, locust bean (carob) gum, tara gum, xanthans, all cellulosics... 

If the pinhead reaction demonstrates chemical damage the next point of interest is to determine the exact cause. The tests described below for damage caused by chemicals or fungi are applicable to all cellulosic fibres. 

Think of a naturally occurring fibre, and it is odds-on that it will be made of cellulose. Cotton, flax, wood, paper, even rayon hre all cellulose the hairs of the cotton seed plant, in particular, are over ninety per cent pure cellulose. There is more of it in the world than any other organic chemical, for it forms the structural framework on which plants (and some bacteria) are constructed. 

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