Preparation and characterization of modified phenolic resin from furfural residue liquefaction

To achieve the high-value utilization of furfural residue (FR), this study innovatively employed a phenol–ultrapure water mixture to liquefy the entire components of FR, obtaining liquefied products (FRP) for the synthesis of modified phenolic resin (FRPF). The physicochemical properties of FRPF resin were systematically evaluated, and its structure and thermal performance were characterized using SEM, FT-IR, GPC, TG, and DSC. The results demonstrated that: 1) Under optimized conditions (20 % substitution rate, 170 °C liquefaction temperature, 2.5 h liquefaction time, and 15 wt% catalyst dosage), the FRPF resin exhibited a wet bond strength of 1.39 MPa and a formaldehyde emission of 1.326 mg/L, indicating its potential as an exterior-grade structural adhesive; 2) The FT-IR spectrum of FRPF resin was similar to that of pure phenolic resin (PF), suggesting analogous structures. However, condensation reactions between FRP molecules resulted in a broader molecular weight distribution and higher Z-average molecular weight. Additionally, the presence of liquefaction residues and sodium sulfate crystals on the resin surface collectively contributed to reduced bond performance; 3) Compared with PF resin, FRPF resin exhibited superior thermal stability. However, its curing onset temperature decreased from 39.55 °C to 35.84 °C, the peak temperature decreased from 55.31 °C to 53.19 °C, and the termination temperature increased from 67.68 °C to 79.63 °C, indicating an earlier initiation but slower reaction progress. This characteristic necessitates longer hot-pressing cycles and higher energy consumption in wood-based panel production. Overall, FRPF resin demonstrates potential feasibility for replacing PF resin. • A phenol-25 % ultrapure water mixture was used as a liquefying agent for the liquefaction of the whole components of furfural residue. • The modified phenolic resin adhesive demonstrates the potential to be used as an outdoor-grade structural adhesive. • The modified phenolic resin adhesive exhibited superior thermal stability compared to the conventional PF resin.