Biostable Cellulosics

The way to increase the enzyme resistance of cellulose ethers is to limit the amount of unsubstituted anhydroglucose units by adjusting the reaction conditions accordingly. In other words, to increase the degree of substitution rather than the molecular substitution, as is shown in this Fig. 6. The resulting cellulose ether is known as biostable or "B"-grade material. 

Chem. Descrip. Polyanionic cellulose Uses Rheology control agent in latex paints, wallpaper adhesives Features Enhanced chem. resist, and biostability Properties Powd. vise. 100-200 mPa-s-(2%)... 

For example, the values of biostability of cellulose calculated from this expression (humidity, 0 = 98%) was equal to 0.5 x 10 s cm dyn p whereas this parameter calculated for polyethylene was 5 orders of magnitude higher 0.4 x lO" s cm dyn pg -... 

Bast fibers contain a bit lower amount of cellulose (about 70%) than cotton ones. Moreover, they contain such components as lignin (10%), wax and trace amonnts of antibiotics, some of which increase biostability of the fiber. The presence of lignins induces coarsening (lignifications) of plant cells that promotes the loss of softness, flexibility, elasticity, and increased friability of fibers. 

Biostability of cellulose fibers is highly affected by further treatment with finishing solutions (sizing and finishing) containing starch, powder, resins and other... 

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