Pulp cellulose , degree

R wPrior to World War II, CN was produced mainly from cotton linters because of their higher degree of purity (alpha cellulose >98%). The high purity linters allowed a higher yield and better quaUty product compared to those obtained from less pure wood pulps or other cellulose sources. The development of highly purified chemical-grade wood pulps has allowed this material to be used in the same manner as are linters. 

Bleached cotton stalk pulp is treated with different concentrations of ethylene diamine (50-100%) for 20 min. It is clear that the crystallinity index (CrI) of these treated pulps is decreased by increasing the concentration of ethylene diamine that is, the decrystallization increases. The degree of polymerization is nearly the same, but some increase is shown in the sample treated with 100% ethylene diamine. This indicates that 100% ethylene diamine may act as a dissolving agent for low degree of polymerization (DP) of cellulosic chains and hemicellulose. 

The grafting reaction depends upon the degree of substitution as well as the kind of pulp used. Introducing acetyl groups in the cellulose chains (high substitution) causes a large reduction of its swellability, which reduces the diffusion of the reactants. Thus, acetylation lowers the graftability of the cellulose. 

The use of xylanases in the preparation of high-purity cellulosic materials requires that the enzyme preparations be free of any cellulase contamination. Treatments of pulps with xylanase preparations containing cellulases have resulted in damage to cellulose fibres as revealed by a drop in pulp viscosities (12,14,17). Similar pulp treatments in which cellulase-free xylanases were used resulted in increases in pulp viscosities (10,18,19). We have shown recently that an apparent increase in the degree of polymerization of cellulose treated with a cellulase-free xylanase is likely due to the selective removal of xylan, leaving an enriched cellulose residue (20). 

Highly purified cellulose wood pulp (greater than 95% alpha cellulose) is the basic raw material for making cellulose acetate. The natural polymer, cellulose, in wood pulp has a degree of polymerization of 500 to 1000, the basic repeating unit of which is cellubiose ... 

Copper Value (Copper Index or Copper Number) of Cellulose It represents the amt of Cu reduced from the cupric to cuprous state in alkaline sola by lOOg of cellulose (such as cotton). In case of cotton, it gives an indication as to whether any appreciable changes have taken place during purification proceduresjin case of woodpulp, it indicates the degree of purity. Accdg to Doree (Ref 4 pp 26 32-3)>normal cotton cellulose has copper values below 0.2 while sulfite pulp has value>2. The alpha-cellulose obtd from sulfite pulp had a value of 0,8... 

Cellulose can be oxidized to different degrees of C6-aldehyde content by photolysis of the 6-azido-6-deoxy derivatives [51]. The / -elimination reaction of the 6-aldehyde (Scheme 2) may lead to terminal double bonds exhibiting a UV absorption Umax = 250 nm) [52,53]. With model C6-aldehyde celluloses, /3-elimination started at 30 °C at pH 9 at elevated temperatures (80 °C) -elimination was detected already at very low pH levels (pH 3.5). Similar results were obtained with HOCl-oxidized pulps, with -elimination starting at room temperature at pH 8.5 (unpublished results). 

At first, a water suspension of pulp has to go through a mechanical treatment that consists of a spring-loaded valve assembly (refiner), where the slurry is pumped at high pressure. The formed MFC is moderately degraded and extremely expanded in surface area. In recent years, cellulose with a nanoscale web-like structure (Fig. 4c) has been made. The fiber diameters are in the range 10-100 nm [19,20]. The degree of fibrillation depends on the number of passes through the refiner (Fig. 4b, c). 

THE TERM PULP is used to describe theraw material for the production of paper and allied products such as paper-board, fiberboard, and dissolving pulp for the subsequent manufacture of rayon, cellulose acetate, and other cellulose products. More specifically, pulp is wood or other biomass material that has undergone some degree of chemical or mechanical action to free the fibers either individually or as fiber bundles from an enbodying matrix. Paper,... 

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