Pine Bark Tannin-Based Resins for Wood Composite Applications.

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Materials

Background:

• Phenol-resorcinol-formaldehyde (PRF) resins are widely used adhesives.
• There is a growing need for sustainable and biobased alternatives to traditional petroleum-based chemicals in resin production.

Purpose of the Study:

• To investigate the potential of pine bark tannins as a partial or full substitute for phenol in PRF resins.
• To evaluate the properties of PRF resins and wood composites modified with different pine bark tannins.

Main Methods:

• Hot-water extraction of tannins from Pinus ponderosa, Pinus radiata, and commercial maritime pine bark.
• Characterization of tannins using TGA, FTIR, ESI-MS, and NMR.
• Preparation of PRF resins, tannin-PRF hybrids, and wood composites.
• Evaluation of adhesive properties via lap shear tests and composite characterization (thermal, mechanical, rheological, water absorption).

Main Results:

• Pine bark tannins exhibited distinct chemical structures and thermal properties.
• PRF and Pinus ponderosa tannin (PT)-PRF resins demonstrated excellent adhesive properties.
• PT-PRF hybrid composites showed enhanced thermal stability, char formation, flexural strength (37.0 MPa), and modulus (4.51 GPa).
• PT-PRF composites exhibited improved dimensional stability with lower water absorption compared to neat tannin systems.

Conclusions:

• Pinus ponderosa bark tannin is a promising biobased alternative for high-performance wood adhesives.
• Hybridization with PRF enhances the reactivity, thermal robustness, and mechanical performance of tannins.
• This research highlights a sustainable pathway for developing advanced wood composite materials.