Revitalization of Industrial Hemp Cannabis sativa L. var. sativa in Slovenia: a Study of Green Hemp Fibres

Abstract

© 2017, University of Ljubljana. All rights reserved. The importance of industrial hemp as a source of highly valuable textile fibres is briefly presented through its use for textiles and composites and its increasing cultivated areas in the 21 st century. On the territory of present Slovenia, about 160 ha of agricultural area was cultivated with hemp before WWII, then it quickly began to decline and at the end of the 1970s, it was no longer cultivated. Revitalization of industrial hemp in Slovenia with field experiments started already in the years 2000/2001 for producing seeds, whereas hemp fibres were used only as an insulation for buildings. The textile technological properties of hemp fibres from different varieties grown in Slovenia have not been examined till now. They are important for using hemp fibres in highly valuable textile products. The properties of green hemp fibres extracted mechanically from non-retted hemp stems of Cannabis sativa L. var. sativa (varieties: Novosadska, Juso-11, Bialobrzeskie, Unico-B and Beniko) were determined. All the analysed varieties except Beniko had stem height over 200 cm. The highest yield of green fibres was 33.1% (Novosadska). The analysed green fibres’ content was 1.24–3.26% of ash, 7.77–8.50% of moisture regain, 10.69–13.92% of water-soluble substances and 8.45–10.83% of pectin. Through a biodegradation process of retting green hemp fibres in tap water at temperature 35°C, 9.01–18.89% of dry mass was removed after ten days. Average linear density of green hemp fibres was very high, around 200 tex. Tenacity of fibres’ bundles was in the range of 167–272 MPa, but tenacity of elementary fibres was 548–672 MPa. From the curves of specific stress-strain, it is seen that green hemp fibres from all five varieties had similar superstructure. All analysed green hemp fibres had high linear density and low mechanical properties. For textile application, they should be further processed into finer fibres in order to increase their tensile stress and become also more flexible and soft.