Wide-angle X-ray scattering studies on contemporary and ancient bast fibres used in textiles – ultrastructural studies on stinging nettle

Stinging nettle ( Urtica dioica ) is a potential source material for industrial applications. However, systematic research on the ultrastructural properties of nettle fibres is lacking. Determining the ultrastructure of nettle and the other bast fibres also provides new insights into the studies of archaeological fibres and their usage. In this study, the nanostructure of modern and ancient nettle samples was studied using wide-angle X-ray scattering (WAXS) and compared to other bast fibres. The culturo-historical fibre samples consisted of nettle, flax, and hemp from White Karelian textiles collected 1894 as well as of 800–900-year-old archaeological textile fragments from Ravattula Ristimäki burial site, Finland. Using WAXS, the average cellulose crystallite widths, relative crystallinities and orientational order (including microfibril angle for the modern fibres) were determined and compared. The results also revealed the suitability of the WAXS analysis for fibre identification. The crystallite widths were of the similar size for all modern fibres (3.4–4.8 nm). Subtle differences in the relative crystallinities in descending order (from flax to nettle, and finally hemp) were observed. Also, subtle differences in the mean MFAs were observed (10 ± 1° for flax, 12 ± 1° for nettle, and 14 ± 1° for hemp). For the culturo-historical fibres, the values for crystallite widths and relative crystallinities were larger compared to the corresponding modern references. In addition, features due to the presence of non-cellulosic, crystalline substances (e.g., calcium oxalates) were detected in the WAXS patterns of all the modern nettle fibres. These features could potentially be used as a tool for identification purposes. Graphical abstract