Cellulose fibrils: Isolation, characterization, and capability for technical applications

Cellulose fibril aggregates embedded in a lignin matrix in the cell wall are a predominant reason for the outstanding specific tensile strength of wood. In order to convert these mechanical properties to practical use for polymer composites, the fibrils can be isolated out of sulphite pulp. The obtained fibrils have diameters below 100 nanometer and lengths in the micrometer range. Homogeneous, translucent fibril films and polymer composites with hydroxypropyl cellulose can be prepared. For mechanical characterization tensile tests and nanoindentation experiments were carried out. The addition of fibrils led to an up to three times higher modulus of elasticity and an up to five times higher tensile strength of the polymers. Network formation was identified by Transmission Electron and Atomic Force Microscopy in films with a filling ratio of at least 10 %. The perspectives of producing new bio-based nanomaterials are promising.