Novel Electrohydraulic Technique of Cellulose Fiber Production from Industrial Hemp

The key stage of processing high-cellulose hemp raw materials is delignification—the removal of lignin and hemicelluloses to obtain strong cellulose fibers. This study experimentally demonstrated the effectiveness of using the electrohydraulic effect (EHE) to delignify high-cellulose hemp raw material, which can then be used as a base for composite materials. Hemp raw material, in the form of 50 mm-long straws, was placed in a water-filled chamber and exposed to a shock wave generated in the water by an electric discharge with an energy of 1.6 kJ at a voltage of 50 kV. The tensile strength of the treated fibers after combined processing (NaOH/EHE) and after EHE reached 262 MPa and 201 MPa, correspondingly, which are 5% and 37% higher than after chemical delignification in a NaOH medium (191 MPa). Cellulose materials obtained from cellulose fiber after EHE exhibit higher strength properties compared to materials based on cellulose obtained by delignification in a NaOH medium. Thus, the tensile strength (σ) of materials made from fibers after EHE was 4.37 MPa, after combined NaOH/EHE treatment 1.94 MPa, and after alkaline treatment 3.95 MPa. EHE reduced delignification time by 2–20 times compared to NaOH treatment and eliminates the need for an additional fiber separation procedure. The use of EHE is proposed as a highly cost-effective, technologically and environmentally sound solution for producing hemp fiber for use in biocomposites, woven, and non-woven materials.