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Methods & Facilities

Chemical analysis

Knowledge of the composition of fibre cell walls is important in relation to the properties. For product and process improvement the understanding of chemical and physical behaviour is essential. Methods to analyse and characterise the structural elements in the fibre cell wall have been elaborated and improved.

Plant cell walls are composed of different polysaccharides and lignin. These components have different properties and functions in the fibre tissues. They can be hydrophilic or hydrophobic, amorphous or crystalline, branched with side chains or contain functional groups.

  • Cellulose is a linear and highly crystalline polysaccharide with a high degree of polymerisation in the native state, insoluble in water, and forms the major structural polymer in plants. The strength properties of plant fibres are largely determined by their cellulose content. Cellulose fibres form the major constituent of wood and wood products, paper and boards, and some of the commercial textile fibres (cotton, flax-linen, and hemp).
  • The non-cellulosic cell wall polysaccharides in plants are classified as hemicelluloses and pectins. These are more complex polysaccharides that are involved in structural integrity and other vital functions. These polysaccharides may be composed of sugars other than glucose and are often branched, or contain substituents and functional groups. The role of these polysaccharides in the cell wall is to glue structural elements together and provide barrier properties, give flexibility and regulation of moisture uptake.
  • Lignin is derived especially from the woody or bark tissues in plants, where they play a role as a glue and matrix for cellulose fibres giving strength and stiffness. Lignin is insoluble in water and requires chemical degradation for solubilisation. In contrast to most biopolymers, lignin is non-linear and not composed of distinguished repeating structural elements. Lignin is a group of three-dimensional complex polymers consisting of phenylpropane units that are crosslinked in various ways and may be condensed to form a dense hydrophobic barrier, protecting the plant from invasion and disintegration. The bonds in lignin can be of ester or ether type, but also aliphatic or aromatic carbon-carbon linkages occur.
    Liquefaction of lignin/wood at elevated temperatures results in thermosetting resins that can be converted to moulded products, adhesives, or carbon fibre. Lignin is released in large quantities in the paper industries when cellulose fibres are extracted from wood. Most of the millions of tons potentially available are not used but rather disposed of by burning and generation of energy.

We are equipped with advanced tools (NMR, mass spectrometry, FT-IR, NIR, X-ray diffraction, etc.) to perform detailed structural analysis. Protocols are available for polysaccharide and lignin identification.

Further reading:

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Morphological analysis

The morphological structure of fibre cells has been studied in relation to fibre formation in the plant and fibre properties for application development. Access to the most advanced light microscopic and electron microscopic techniques provides detailed information about fibre dimensions and architecture, peculiarities, or defects. Specific staining for localisation of lignin or other cell wall components reveals distribution profiles and aberrations in structure due to processing conditions or deliberately introduced modifications.

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Physical properties

The physical properties of fibres determine their suitability in applications. Together with fibre dimensions (fineness, length), physical properties like fibre strength, stiffness, elongation, surface characteristics, and swelling are most important quality aspects for technical use. Thermal stability and resistance to (bio)degradation are relevant for processing conditions or determining the functional life time of a product. Homogeneity and colour can be critical in textile processing.

Methods for determination of physical fibre properties are available.

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