Study of solutions to optimize the extraction of hemp fibers for composite materials

Abstract

Fibres from hemp stems can be extracted through different mechanical processes following dew or water retting etc. Extraction processes generally have a significant impact on mechanical and morphological properties of the fibres. In this study, hemp fibres are extracted following three different ways. In the first route hemp fibres are extracted from FUTURA 75 variety stems by performing scutching, hackling and microwave degumming. A second batch of fibres of the same variety was extracted by scutching and hackling after an initial microwave degumming treatment. In the third route, the same variety of hemp fibres are extracted from dew retted stems grown at Piacenza (Italy). Finally, the mechanical properties of single fibres as well as the fineness of technical fibres of all types of extracted fibres are evaluated and compared and the interest of the microwave degumming for hemp stem is evaluated.

Properties of Frost-Retted Hemp Fibers for the Reinforcement of Composites

“…Regarding unitary fibers, in spite of their high cellulose content observed during the chemical composition analysis in the section 5.1, the average value for apparent modulus (16.6 ± 8.5 GPa) is in the lower range of the data from the literature (14.4-51 GPa (Bourmaud et al 2018;Gregoire et 2019)), and the average value for the strength (500 ± 239 MPa) is in the middle range of the data available in the literature (285-969 MPa) (Bourmaud et al 2018). The relatively low mechanical properties might be related to the low lignin content measured in our fibers from the Tisza variety compared to the values usually reported for Western European hemp varieties.…”

“…Prior to the decortication, the straws can undergo a retting process (1) to loosen bonding between fiber-fiber and bundle-bundle by degrading the non-cellulosic components in the bast fiber layer, particularly the pectic polysaccharides (Horne 2020); and (2) to facilitate fiber separation and to avoid fiber breakage during following mechanical processing (e.g. scutching) and to preserve the fibers quality (Gregoire et al 2019). Western European field retting consists of leaving purposefully the stems in the field after the autumn harvest to be decorticated under the actions of microorganisms.…”

Extraction of cellulose fibers from flax and hemp: a review

“…Polar molecules interact with oscillating microwave and radio frequency radiation by undergoing rapid rotations, which generates thermal energy (termed dielectric heating) in proportion to the level of interaction. That enables a degree of selectivity as pectin is more polar than cellulose and thus heats up and is degraded at greater rates (Gregoire et al 2019;Nair et al 2015). Physical separations of the pectin from the cellulose are also likely.…”

Recycled Cellulose Fiber Reinforced Plaster

“…The addition of natural fibers in plaster strengthens the plaster coating and thus enhances ductility. Over the last decades, lignocellulosic or cellulosic fibers derived/extracted from various plants (abaca, coir, cork, flax, hemp, rice straw, and sisal) have been used in plaster mortars/composites [ 6 , 8 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. The use of a combination of two natural fibers (kenaf and sisal) for the reinforcement of lime plaster was studied in [ 26 ].…”