Production of Fiberboards from Shives Collected after Continuous Fiber Mechanical Extraction from Oleaginous Flax

Abstract

In this study, fiberboards were produced from shives collected after continuous fiber mechanical extraction from oleaginous flax straw. Fiberboards were produced through thermo-pressing, and their mechanical and thermo-mechanical properties were studied, as well as their water resistance. The influence of one pretreatment for shives and lignin addition was investigated on the different properties. Boards obtained were all cohesive hardboards. The optimal board was obtained from fibers extruded from shives and without addition of any supplementary lignin amount. Looking at its characteristics and standard NF EN 312, the latter perfectly complied with the requirements for type P1 boards, i.e. boards for general uses in dry conditions. RÉSUMÉ : Dans cette é tude, des panneaux agglomérés de fibres ont été produits à partir d'anas collectés aprè s extraction mé canique des fibres libé riennes de paille de lin olé agineux. Les panneaux ont été mis en oeuvre par thermopressage. Leurs propriétés mécaniques et thermo-mé caniques ont é té é tudié es ainsi que leur comportement vis-à-vis de l'eau. L'influence d'un pré traitement thermo-mécanique des anas bruts à l'aide d'une extrudeuse bi-vis a é té é tudié e ainsi que l'ajout de lignine exogène. Tous les panneaux mis en oeuvre possèdent une tenue suffisante pour ê tre manipulé s à la main. Le panneau ayant obtenu les proprié té s optimales a é té obtenu à partir des anas extrudé s et sans ajout supplé mentaire de lignine. Au regard de ses caracté ristiques et du standard NF EN 312, ce dernier remplit complètement les critères d'un panneau aggloméré de type P1 (panneau d'usage général utilisé en milieu sec).

Twin-Screw Extrusion Process to Produce Renewable Fiberboards

“…A comparison of the usage properties of board numbers 1, 3, and 7 also shows the beneficial effects of higher applied pressure during molding on these properties, whether it is the flexural strength, the Shore D surface hardness, or the water resistance of the material after immersion. As the pressure increases, the mobilization of the lignin-based binder is promoted 27 . In the molten phase, its viscosity is reduced, and wetting of the fibers is optimized.…”

“…However, this reduction in thickness swelling remains insufficient. For future work, other additional processes, e.g., coating, chemical, or steam treatment, after hot pressing should be tested to improve this dimensional stability parameter 27 to a greater extent. Another original solution could be the addition of hydrophobing agent(s), e.g., vegetable oil derivatives, to the premix directly in the twin-screw extruder.…”

“…For the defibration of lignocellulosic materials to produce fiberboards, the most recent works have used rice straw 25 , 28 , coriander straw 26 , 29 , oleaginous flax shives 27 as well as sunflower 30 , 32 and amaranth 31 barks. The current interest of lignocellulosic biomasses for such an application (i.e., mechanical reinforcement) is explained by the regular depletion of forest resources used for producing woodbased materials.…”

“…Mechanical, thermal, and chemical 35 or even enzymatic 36 , 37 , 38 pre-treatments must be applied. These steps also increase self-adhesion of fibers, which can promote the production of binderless boards 27 even if an exogenous binder is most often added.…”

“…However, their water resistance was found to be lower: 71% and 87%, respectively, for thickness swelling. Self-bonded panels based on extrusion-refined shives from oleaginous flax straw can also be obtained 27 . In this case, it is the ligneous fraction, released during the twin-screw TMC defibration, that contributes to the self-bonding.…”