Properties of cellulose pulps from acidic and basic processes

Research has intensified in recent years on organic solvent pulping processes to supplement or replace conventional pulping processes. One of the main problems with organosolv pulps is the inferior tear strength compared to kraft pulps. An investigation of the properties of two acidic (acetic acid organosolv and acid sulfite) and one basic white spruce pulp (kraft) was carried out to determine factors affecting differences in tear strength. Properties evaluated were lignin and sugar content, mineral composition, ESCA oxygen-to-carbon ratios, acid-base characteristics, water wettabilities, degree of polymerization and crystallinity of cellulose, fiber length and coarseness, and physical properties of the various pulps. Differences in tear strength have been attributed to degradation and changes in the cellulose structure, the hemicellulose-lignin matrix in which the degree of polymerization of hemicelluloses plays the most important role in low yield pulps, and finally, the bonding capacity of the fiber surfaces.