Rheological Characterization of Lyocell Solutions

The primary goals of the study were to prepare lyocell solutions from different wood pulps. An individual specific Protocol was developed for lyocell solution preparation from different cellulose sources. The cellulose sources included bleached hardwood and bleached softwood pulps. Rheological measurements were used to characterize the behaviour of lyocell solutions, i.e. cellulose dissolved in N-methyl morpholine N-oxide (NMMO) monohydrate. Complex viscosities were measured and influence of parameters such as cellulose source, concentration, DP (function of molecular weight) and temperature were studied. The dominance of viscous behaviour, G' values, over elastic behaviour, G" values, is affected by pulp type, concentration, molecular weight and degrees of polymerization (DP). At lower concentrations and degrees of polymerization, dissolving pulp solutions show viscous, inelastic behaviour at low frequencies. At higher concentration and DP, dissolving pulp solutions are more elastic at higher frequencies.