The rheological properties of pulps during acetylation process were discussed by using the rotationalviscometer. Cotton linter, commercial wood pulp for acetyl-cellulose and Viscose, purified wood pulps which were treated by hot alkali, cold alkali or acid hydrolysis, and pentosan were used. The rheological properties which were estimated from their rheogram is different by pulps respectively. And viscosities of their acetylation products were also examined.
Higher reactive pulps for acetylation changes, generally, their flow properties from non-newtonian flow to Bingham flow at early stage of acetylation than poorer one. Cotton linter changes most rapidly his flow properties and also have lower apparent viscosity of acetylation mixture than any pulps., But wood pulp which was hydrolyzed with mild condition and xylan do not change their non-newtonian flow properties during acetylation. And also wood pulp which was mercerized and then hydrolyzed with hard condition, did not exhibit the non-newtonian flow and always took a Bingham flow from beginning to end.
From these results, it seems that this difference of rheological behavior between cotton linter and wood pulps may depend upon the difference of their fine structure and the presence of non-cellulosic materials in them. And on account of these differences wood pulp may take a poorer dispersity of his acetylation bath.
This poorer dispersity of the acetylation bath of wood pulp causes higher viscosity than cotton linter for their accetylation products in the same solvent. It is said that wood pulp has a higher viscosity ratio (27%/7%) than linter. This difference of their viscosity ratio may depend also upon the poorer dispersities of wood pulps in the acetylation mixture.