Synthesis and characterization of bio-based phenol-formaldehyde resol resins from bark autoclave extractives

摘要

With the growing concern for fossil fuel depletion and environmental carbon footprint, there is a strong interest in exploring the renewable biomass materials as substitutes for petroleum-based feedstock. In this study, bark autoclave extractives from the mountain pine beetle (Dendroctonus ponderosae Hopkins) infested lodgepole pine (Pinus contorta Dougl.) was used for partially replacing petroleum-based phenol in the phenol-formaldehyde (PF) resol resin formulation. The structural characteristics of the bark autoclave extractives were examined using liquid-state ~(13)C NMR. The curing behavior and curing kinetics, bonding strength and bond development of the resulting bio-based bark extractive PF resol resins were investigated using DSC, lap-shear and DMA tests, respectively. Results showed that bark autoclave extractives were a complicated mixture containing tannin, degraded hemicellulose and degraded lignin components. The bark extractive-PF resins exhibited higher molecular weight, higher viscosity, shorter gel time and faster curing rate than the lab-made PF resin without bark components. The bark extractive-PF resins had comparable bond strengths to a commercial PF resin even when the phenol replacement rate was as high as 50%. The bark autoclave extractives obtained from the beetle-infested lodgepole pine barks is suitable as a partial replacement of petroleum-based phenol in making PF resol adhesives.