Cellulose-based polymers ethylcellulose

This class of cellulose derivatives includes hydroxypropylmethylcellulose or HPMC, hydroxyethylcellulose (58), methylcellulose, HPC, and ethylcellulose. As mentioned earlier, most cellulose-based polymers except for PVP, have lower surface tension values in the range of 40-50 mN/m, thus similar adhesive and film-forming qualities will be seen. 

Ethylcellulose is an ethyl ether of cellulose, prepared by ethylation of the alkali cellulose, whose most important property is to be insoluble in water. Different ethylcelluloses are commercially available varying both the ethoxyl content (45.0-49.5%) (Ethocel , by Dow Chemical Company) and viscosity values (10-100 cP). As a general rule, viscosity increases as the molecular weight (MW) of polymer increases. The lower viscosity grades of this polymer are more compressible and compactible, leading to harder tablets and, consequently, to lower drug dissolution rates [14-16], This increase in com-pactibility has been explained based on the fact that the polymers with lower MW show a less ordered structure [14]. 

P. are viscous liquids, which are either strongly alkaline, aqueous solutions that contain - methyl-cellulose or acrylic polymers as thickener or are solvent-based (e. g., methylene chloride) and neutral. The latter are thickened by ->methylcellulose of high DS, - hydroxyethylcellulose, - hydroyx-propylcellulose and their mixed ethers (- cellulose ethers). Some contain - ethylcellulose. 

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