Cellulose derivative viscosity

Cellulose may be solubilised by treatment with sodium hydroxide and carbon disulfide. It can be regenerated by acidification of the solution. This is the basis of the production of regenerated cellulose fibre, so-called viscose rayon , which is a major textile fibre. The technique is also used for the production of continuous cellulose-derived film, so-called cellophane (from cellulose and diaphane , the latter being French for transparent). 

Although untreated starches do not swell sufficiently, certain modified forms, such as sodium starch glycolate, do swell in cold water and are better as disintegrants. Various cellulose derivatives, including methylcellulose and carboxymethylcellulose, have been used in this role, but with limited success due to the marked increase in viscosity they produce around the dispersing tablet mass. 

As a result of these studies it became evident that mechanical and chemical treatments may alter the relative amounts of crystallized and amorphous cellulose in a sample. For example, it was estimated that a normally coagulated viscose filament was about 40 % crystalline and 60 % amorphous while filaments of the same material, after being stretched, appeared to be 70% crystalline and 30% amorphous. This effect was observed to be more pronounced in cellulose derivatives than in unsubstituted cellulose where apparently the blocking of hydroxyl groups reduces the lateral forces of cohesion between chains, facilitates slipping and consequently promotes parallelization of chains. 

If micelles were present in both types of solutions, we would have to assume different forces binding different cellulose derivatives, hence viscosity measurements should give different molecular weights. However the results disagree with those obtained by Gralen and Svedberg [32a], and reported on p. 343. 

The physicallydried binding agents include acrylic resins, polyesters, silicones, cellulose derivatives and others. Polyamides and polyolefins are used as raw material for powder lacquers. Differing from physically dried lacquers, chemically dried lacquers contain crosslinked macromolecules. The raw materials used as binding agents can in this case be used without solvents because of their low viscosities and react with the substrate by one of the above mentioned polymerization reactions. 

In summarizing the intrinsic viscosity relations presented in this section, it must be admitted that they represent nothing more than rather small semi-empirical refinements of the Flory excluded volume theory and the Flory-Fox viscosity theory. For a large fraction of the existing body of experimental data, they offer merely a slight improvement in curve-fitting. But for polymers in good solvents it is believed that a more transcendental result has been achieved. The new equations permit more reliable assessment of unperturbed chain dimensions in such cases, and in some instances (e. g., certain cellulose derivatives see Section III B) they offer possible explanations of heretofore paradoxical solution behavior. 

Draining corrections have not been applied to any of the data for other cellulose derivatives, as they are in all cases smaller than for the nitrate. The results of the viscosity calculations for these substances arc... 

The first man-made fibers of commercial importance were the cellu-losics. With respect to regenerated cellulose fibers, viscose rayon predominates. Between 1900 and 1967, world production of viscose rayon rose from 1000 tons to 2,700,000 tons (3). Cellulose derivative fibers did not go into commercial production until the 1920s. At that time cellulose acetate was manufactured. Cellulose triacetate fiber was brought into commercial production in the United States in 1954 (4). 

There are two basic types of methylcellulose viscometers— one for cellulose derivatives of a range between 1500 and 4000 centipoises, and the other for less viscous ones. Each type of viscometer is modified slightly for the different viscosities. 

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