Performance enhancement of wood composites using cellulose-reinforced cornstarch–tannin adhesives derived from electrical-assisted extraction

Abstract

This study investigates the impact of electrical-assisted extraction techniques on cellulose derived from almond shells and its performance in formaldehyde-free cornstarch–mimosa tannin (CM) adhesives. Cellulose was extracted using three methods: conventional alkali treatment (AT), alkali treatment assisted by pulsed electric fields (PEF), and alkali treatment assisted by high-voltage electrical discharges (HVED). Comprehensive analyses, including FTIR, XRD, TGA/DTG, DSC, and SEM, were conducted to evaluate the chemical structure, crystallinity, thermal stability, and morphology of the extracted celluloses. The results revealed that while cellulose yield varied slightly among treatments, electrical-assisted extraction significantly enhanced delignification and fibrillation without altering the cellulose I crystalline structure. Both PEF- and HVED-treated celluloses exhibited improved crystallinity (≈59%) and thermal stability (T_onset ≈ 303 °C), indicating superior structural integrity. Incorporation of these celluloses into CM adhesives increased viscosity, solid content, and shear strength, with optimal performance at 6 wt% cellulose loading. Particleboards bonded with HAC-CM adhesives showed the highest mechanical properties (IB = 0.79 MPa, MOR = 32.27 MPa, MOE = 3125 MPa), exceeding EN 312 (P4) standard requirements. Water absorption and thickness swelling were markedly reduced, confirming enhanced moisture resistance. Overall, HVED-assisted extraction produced cellulose with superior reinforcing capability, demonstrating a sustainable and high-performance pathway for developing formaldehyde-free wood adhesives from agricultural residues.