Insight Understanding the Replacement Effect of Enzymatic-Hydrolysis Residue Instead of Phenol for Preparing Phenol-Formaldehyde Adhesive

In order to valorize the enzymatic hydrolysis residues (EHR) from the bioethanol industry, this work studies the effects on the structure, properties as well as shear resistance of EHR-based phenol formaldehyde (EPF) adhesives prepared from EHR instead of commercial phenol. 2D heteronuclear signal quantum coherence NMR (2D HSQC NMR) and ³¹P NMR analysis reveal that lignin in EHR (EHL) possesses a high amount of G and H units which contain 1.9 mmol g⁻¹ active sites (reaction site with formaldehyde). Fourier-transform infrared (FT-IR) characterization shows that the instead proportions of EHR with 5–30% in EPF adhesives do not show great influence on the chemical structure type and main functional groups of the prepared adhesives. The shear strength measurement results show that the strength of the 10%-EPF adhesive is significantly improved by 29% compared to phenol-formaldehyde (PF) adhesive, which is due to EHL in adhesives enhanced the cross-linking of polymer chains. This work emphasizes the potential benefits of using industrial EHR to develop cost-effective phenol formaldehyde adhesive preparation schemes, therefore giving an additional value to waste from biorefineries.