Cellulose acetate polymerization degree

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 ... 

Several polymers were found to fit all or most of the above criteria and were used to prepare the carrier films. Many polymers have been used for this purpose, viz., ethyl cellulose, poly(y-benzyl glutamate), poly(vinyl acetate), cellulose acetate phthalate, and the copolymer of methyl vinyl ether with maleic anhydride. In addition to the base polymers, plasticizers were often needed to impart a suitable degree of flexibility. Plasticizers, which are found to be compatible with polymeric materials include, acetylated monoglycerides, esters of phthalic acid such as dibutyl tartarate, etc. An excipient was usually incorporated into the matrix of the carrier films. The excipients used were water-soluble materials, which are capable of creating channels in the polymer matrix and facilitate diffusion of the drug. PEGs of different molecular weights were used for this purpose. 

Threshold volume fractions observed for cellulose acetate (CA and CTA), ethyl cellulose (EC) and hydroxypropyl cellulose (HPC), each in various solvents, are presented in Table 3. The results depend to some extent on the solventThe data included are not exhaustive. Other cellulose esters exhibit mesomorphic behavior Chanzy et al. observed mesomorphic behavior in solutions of cellulose itself when dissolved in N-methylmorpholine N-oxide containing water at concentrations of cellulose in the range 20-55 % w/v, depending on the temperature, the water content of the solvent and the degree of polymerization of the cellulose. Solutions of cellulose in mixtures of trifluoroacetic acid with 1,2-dichloroethane or with chloroform are hkewise lyotropic at concentrations of 20% (w/v) and above according to Patel and Gilbert... 

Viscosity (dynamic) various grades of cellulose acetate are commercially available that differ in their acetyl content and degree of polymerization. They can be used to produce 10%... 

The cellulose acetate used commercially for acetate yam has an acetyl content of about 39.5 per cent and has a degree of polymerization of about 400. Material of this composition is soluble in acetone, and spinning dopes of about 25 per cent solids concentration can easily be prepared. Materials having a 39-41 per cent acetyl content can be made into plastics by compounding the cellulose acetate with plasticizers such as diethyl phthalate. Cellulose triacetate (43.0-44.8 per cent acetyl content) is finding increased commercial use. By coating from appropriate solvents, a film base of greatly improved phj ical properties has been produced. Triacetate yams are now in commercial production. 

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