Hydroxylated graphene-assisted depolymerization of Acacia mangium tannin for the preparation of fast-curing and high-strength tannin–phenol–formaldehyde resins

Traditional phenolic resins face challenges, such as high curing temperatures and brittleness, severely limiting their widespread application. This study proposes a partially bio-based strategy, in which hydroxylated graphene (G-OH) is employed for the first time as a green nucleophile to depolymerize Acacia mangium tannin, thereby completely avoiding the use of petroleum-derived and/or toxic nucleophiles. The resulting depolymerized tannin is used to replace 50% of phenol in the synthesis of phenolic resins. This innovative approach resulted in a substantial reduction in the average polymerization degree of the depolymerized tannin (GOH-DAMT), decreasing from 9 to 2. The low molecular weight and high reactivity of GOH-DAMT considerably accelerate the curing speed of GOH-DTPF, reducing the initial curing temperature from 157.9 °C to 136.9 °C. The increased reactivity of GOH-DAMT enhances the resin’s cross-linking density, while the uniformly dispersed nanosheets effectively facilitate the transfer of interfacial stress. The bonding strength of GOH-DTPF cured at 115 °C met the Class I plywood production requirements (GB/T 9846 − 2015, ≥ 0.7 MPa), while the bonding strength of GOH-DTPF cured at 120 °C and 130 °C increased from 0.78 MPa and 0.95 MPa for TPF to 1.15 MPa and 1.30 MPa respectively, surpassing those of PF (0.97 MPa and 1.12 MPa). Furthermore, GOH-DTPF exhibited a 155% increase in the work of adhesion compared to PF, demonstrating high toughness. These advancements highlight the potential of GOH-DTPF resins for a broader range of applications in wood-based composites and their promise for sustainable industrial use.