Functional Cellulose Materials

Cellulose fibrils in the cell wall of plant fibers are responsible for their extraordinary high tensile strengths. These fibrils or fibril bundles are isolated out of wood and other lignocellulosic fiber sources with diameters in nanometer and lengths in micrometer scale (microfibrillated cellulose, MFC). They are used for the reinforcement of matrices or for the elaboration of innovative functional materials. In our Lab, MFC finds applications in hydrogels, aerogels, packaging, nanopapers, membranes, fibers, (bio)polymers like adhesives, coatings or sealants, as well inorganic matrices.

Microfibrillated Cellulose (MFC)
In Nature, cellulose is composed of  ß (beta)-1,4 linked glucopyranose units, with polymer chains associated by hydrogen bonds forming bundles of fibrils, also called microfibrillar aggregates, where highly ordered regions (i.e., crystalline phases) alternate with disordered domains (i.e., amorphous phases) inside plant cell walls.
MFC consists of long, flexible and entangled cellulose nanofibers, containing both amorphous and crystalline phases. These nanofibers are isolated in our laboratory from cellulose pulp using a two steps mechanical treatment, involving a refining step followed by a high-pressure homogenization step or grinding. An aqueous suspension of MFC is obtained, from which a typical SEM image is presented, displaying a network of interconnected cellulose microfibrils, with diameters from 10 to 100 nm and aspect ratios from 50 to 100.
Functionalization of MFC
Despite their highly attractive characteristics, these natural nanofibers are strongly hydrophilic, which prevent their use in non-polar environments. To solve this issue and further broaden their scope of applications, we are chemically functionalizing the nanofibers in a controlled manner in order to tune their surface properties. The chemistry of alcohols is mostly envisaged.
Elaboration of porous materials from MFC
Lightweight, flexible and robust cellulosic aerogels/foams can be obtained by replacing water of an aqueous MFC suspension with air, using either vacuum drying, freeze-drying (FD), or CO2 supercritical drying techniques. Together with suitable functionalization pathways, we are synthesizing functional aerogel materials for specific applications.
Microfibrillated cellulose as reinforcing agents in composite applications

Due to its morphology and attractive mechanical properties, MFC is an adequate reinforcing agent for composite applications. In our laboratory, the cellulose nanofibers are incorporated in polar or nonpolar matrices, the latter case often requiring a chemical derivatization of the nanofibers prior to compounding.
In other applications, MFC is used as functional matrix material.
A few examples are listed under current projects.

Competences / methods
  • Mechanical tests (tension tests, dynamic mechanical thermal analysis) 
  •  Light microscopy, force microscopy
  • Scanning and transmission electron microscopy
  • IR-/UV-spectroscopy
  • Dynamic water sorption (DVS)
  • Mechanical isolation of cellulose nanofibrils (inline- and high pressure disperser (Microfluidizer), Masuku Grinder)
  • Wet chemistry (chemical modification)
  •  Freeze drying and Critical point drying
  • Compounding of cellulose nanofibrils/(bio)polymers
  • 3-D Bioplotter
  • 100 l reactor for chemical functionalisation