All-cellulose composites via short-fiber dispersion approach using NaOH–water solvent

All-cellulose composites were prepared by dispersing short softwood kraft fibers in dissolving pulp-8 wt% NaOH–water. The degree of polymerization of the dissolving pulp used for the matrix and the concentration of reinforcing fibers were varied. Morphology, density, crystallinity, cellulose I content and mechanical properties of the composites were investigated. A special attention was paid on the presence of non-dissolved fibers originating from incomplete dissolution of pulp in 8 wt% NaOH–water thus decreasing the actual concentration of dissolved cellulose in matrix solution. This “lack of matter” induced the formation of pores, which strongly influenced the morphology of composites. Density was shown to be the main parameter contributing to the mechanical properties of the prepared all-cellulose composites. The results demonstrate the complexity of the system and the need in taking into account the dissolution power of the solvent.

Morphology of all-cellulose composites: matrix is from low-DP dissolving pulp (a) and from high-DP pulp (b).