1.1 Structure and application of the hemp plant

The hemp plant can reach a height of up to 4 m. The diagram below shows the structure of the hemp plant. On the outside of the stem are the strong bast fibres, commonly known as hemp fibres (Figure below, right). The so called primary bast fibres are, a.o., suitable to produce textile fabrics; the secondary bast fibres are shorter, and therefore less suitable for textiles, however they are suitable for use in fibre reinforced composites and insulation. The high strength (and stiffness) result from the high content of cellulose (about 70 wt.%) and the relatively low angle between the main fibre axis and the orientation of the cellulose molecules in the fibre.^[1]

On the inside, the stem is composed of a woody core material which, after separation from the bast fibres, is know as shives or hurds. In between the bast fibres and the woody material there is a glue layer which is removed during processing (section 5.4, 6.1, 7.1.1).

The stem is hollow inside. At its top there are the flowers, or the seeds later in the season. The weight ratio is approximately 25% bast fibres, 50% shives and 25% for the other crop parts.

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Schematic representation of a fibre hemp plant (left) and the cross-section of a hemp stem (right).

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Microscopy photograph of the transverse section of a piece of fibre hemp stem.

The table below presents an overview of products which can be prepared from different components of the hemp plant, and their applications.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8911747/pdf/materials-15-01901.pdf