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

Abstract Stinging nettle (Urtica dioica) among other bast fibres, is a potential fibre source material for industrial and manufacturing applications. However, systematic research on the ultrastructural properties of nettle fibres is lacking. Determining the ultrastructural parameters of the bast fibres could provide also new insights into the studies of archaeological and historical fibres and their usage. In this study, modern and ancient fibre samples of stinging nettle were studied using wide-angle X-ray scattering (WAXS) and compared to other well-studied plant fibre species. From the WAXS patterns, the mean microfibril angle, average cellulose crystallite width and relative crystallinity index were determined. Besides, the suitability of the WAXS method for fibre identification purposes was studied. The culturohistorical research material consisted of fibre samples of nettle, flax and hemp acquired from White Karelian textiles collected 1894 as well as of 800–900-year-old archaeological textile fragments from Ravattula Ristimäki burial site in Kaarina, Southwest Finland. The crystallite widths for all modern fibres were of the similar size, however subtle differences in the relative crystallinity values in descending order (from flax to nettle and finally hemp) were observed. For the culturohistorical fibres, the values for average crystallite width and relative crystallinity were larger compared to the modern references of the same fibre type. In addition, individual features due to the presence of other crystalline substances (noncellulosic, minerals e.g., calcium oxalates), were detected in the scattering patterns of all modern nettles. These features could potentially be used as a tool to identify modern nettle fibres.