Tobacco Stem Powder‐Modified Phenolated Kraft Lignin‐Based Phenol–Formaldehyde Adhesive for Wood Bonding

ABSTRACT Lignin and agricultural residues are promising resources for wood adhesives, but the use of tobacco stem powder ( TSP ) in phenolated lignin‐based phenol–formaldehyde ( PF ) adhesives remains little studied. Phenolated kraft lignin‐based PF ( PKL ‐ PF ) resin was prepared, and TSP partially replaced concentrated resin solution at constant spread. L 9 orthogonal designs optimized resin synthesis and hot‐pressing. At the selected pressing conditions (140°C, 140 g m −2 , 9 min), dry strength peaked at 10 wt% TSP (4.63 ± 0.72 MPa ), significantly exceeding the TSP ‐free control (3.52 ± 0.35 MPa ). Wet strength was highest at 15 wt% TSP (4.42 ± 0.73 MPa ), but did not differ significantly from the control (4.17 ± 0.47 MPa ). After boiling‐water treatment, 15 wt% TSP gave the highest bonding strength (3.60 ± 0.46 MPa ), whereas 12 wt% TSP had the highest wood failure percentage (74.00% ± 13.42%).