Cellulose mixed

Highly Anisotropic Cellulose Mixed-Ester Membranes for Microfiltration... 

Cotton fiber is made of the epidermal hairs from seeds of members of genus Gossypium. These fibers consist of hollow cylindrical tubes that are 15-22 pm in diameter, narrowing at one end. The walls of a cotton fiber are made of 90-96% cellulose, mixed with about 5% water and small amounts of pectins, and other impurities. When dried, these tubes are flat and naturally curl or twist like a ribbon. Untreated cotton has from 150 to 300 twists per inch. The fibers are from 0.5 to over 2 inches long, and are extremely thin, from 0.0005 to 0.0009 inches in diameter. 

For a wider range of properties, cellulose mixed esters have proved to be superior to the single esters, combining satisfactory strength with increased solubility and resistance to moisture as compared to the acetate. Cellulose acetate propionates and acetate butyrates have become commercially prominent, particularly in the fields of photographic films, plastics and lacquers. 

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. 

Cellulose acetate has offered little in fulfilling the requirements of a protective coating material. Although stable to light, it is restricted in use by its limited solubility in solvents, and its poor compatibility with resins. It has been used only for special purposes as a lacquer material, and to a limited extent for surface coatings on paper and cloth. Cellulose mixed esters appear more promising for th se uses. Cellulose acetate... 

Cine Films must withstand severe mechanical wear and must be of good dimensional stability for projection. Cellulose nitrate has qualities which are very desirable for this purpose, and remains the standard product for the professional moving picture industry. Amateur and educational Cine Films must be made of less inflammable material. Cellulose acetate has been used for this purpose but is limited in its moisture resistance, its strength and its tendency toward brittleness at low humidities. Improvements have been obtained by the employment of cellulose mixed esters possessing a moderate higher acyl content. Such products are widely used for narrow width Cine Films. 

Finishing wood cellulose Other sources of cellulose Drying cellulose before nitration Industrial nitration of cellulose Mixed acids Nitration m pots Centrifugal nitration Thomsons method Nitration with mechanical stirring German method Continuous methods of nitration Literature... 

Carboxymethyl)cellulose mixed human serum albumin 105... 

E.C. powder consists principally of nitro-cellulose mixed with barium nitrate and a small proportion of camphor. 

Cellulose mixed esters contain acetate and propiionate or butyrate groups. They have a balance of properties different, and for some qrplications, superior to the acetates. 

Iwata T., Azuma J., Okamura K., Muramoto M., Chun B., Preparation and NMR assignments of cellulose mixed esters regioselectively substituted by acetyl and propanoyl groups, Carbohyd. Res., 224, 1992,277-283. 

Other two-dimensional techniques, such as correlation spectroscopy (COSY) (118), DEPT (119), Homonnclear Hartmann-Hahn (HOHAHA), sohd state (120), etc, give var5nng degrees of snccess when applied to the structure-property relationship of cellnlose triesters. The recent application of H—multiple-bond correlation (HMBC) spectroscopy for the imambiguous assignment of cellulose mixed esters has successfully demonstrated the utility of NMR for the structiu-e elucidation of complex cellnlose esters (121). It is this unique abihty to provide detailed information on intermolecular interactions of cellulose esters in coatings (115) or in polymeric blends that continues to put NMR spectroscopy well ahead of other analytical techniqnes. 

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