Molecular weight cellulose ether table

The two primary categories of cellulose derivatives, cellulose esters and cellulose ethers, which dominate the markets for cellulose derivatives (O Table 8), have somewhat different raw material requirements. Whereas both types of modification technologies prefer to start with chemical cellulose of high a-cellulose content, ethers give preference to molecular weight considerations while esters are sensitive to impurities. This is a consequence of the predom-... 

Surface tensions of 2% aqueous solutions of commercially used water-soluble cellulose ethers were determined for comparative purposes in the author s laboratory (Table 10). Five derivatives were selected, each with two different molecular weights (nominal viscosity grades). 

Several research groups have successfully used cellulose ethers in solid dispersions. These polymers are hydrophilic in nature and have high molecular weight and good thermal and mechanical properties, which makes them good candidates for HME (Table 4.1). The most commonly used polymers in this family of excipients are HPMC and hydroxypropyl cellulose (HPC). 

This PE is described in the USP as the sodium salt of polycarboxymethyl ether of cellulose. Its typical molecular weight is 90.000-700.000. The rheological properties of CMC depend on the polymer concentration and on the degree of substitution (conversion of -OH into -0-CH2-COO ) which varies from 0.5 to 1.2 [35, 36]. Thus, various grades of CMC with different aqueous viscosities are available, currently regarded as low-, medium-, and high-viscosity (CMC-Na (LV), CMC-Na (MV) and CMC-Na (HV), respectively). At 1 % w/v aqueous concentration they yield the viscosities described in Table 2 [10]. 

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