A tough, strong, and fast-curing phenolic resin enabled by quercetin-functionalized hyperbranched polymer

Phenolic resins are widely utilized in outdoor and structural wood-based panels; however, their high curing temperatures and brittleness have constrained their potential applications. This study developed a fast-curing phenolic resin (HPAQ/PF) with enhanced toughness and strength, achieved by incorporating a quercetin-functionalized hyperbranched polymer (HPAQ) into a phenol-formaldehyde (PF) resin. The HPAQ was synthesized by grafting biomass-derived quercetin onto an amino-terminated hyperbranched polymer. The phloroglucinol structure of quercetin, in conjunction with the amino groups, significantly accelerated the curing process of the HPAQ/PF resin. Consequently, the gel time was reduced from 593 s to 274 s, while the initial and maximum curing temperatures decreased from 155.6 °C and 202.4 °C to 128.7 °C and 171.7 °C, respectively. The moisture uptake value of the HPAQ/PF resin was reduced from 28 % to 7 % compared to the PF resin. The boiling water bonding strength and debonding work of the HPAQ/PF resin were measured at 1.75 MPa and 0.780 J, respectively, which were 51 % and 105 % higher compared to the 1.16 MPa and 0.380 J of the PF resin. These improvements were attributed to the enhanced compatibility and strong interfacial interactions between HPAQ and the PF chains, as well as the unique branched structure and intramolecular cavities of HPAQ. This study presents a simple and effective approach to enhance the curing speed and toughness of phenolic resins.