Bio-oil-based phenol–formaldehyde resin: comparison of weight- and molar-based substitution of phenol with bio-oil

Abstract

The objectives of this study were (i) to synthesize bio-oil-based phenol–formaldehyde resin to be used for the wood products industry, and (ii) to investigate the effect of phenol substitution (molar-based vs. weight-based) with bio-oil on the properties of resulting PF resin. Bio-oil was produced by hydrothermal liquefaction (HTL) process using sweetgum hardwood, and utilized as a bio-based phenolic feedstock as an alternative for petroleum-based phenol in the synthesis of PF resin. Phenol was substituted with bio-oil (both as weight- and molar-based). The resulting PF resin was noted as BPF-W and BPF-M when bio-oil was used to replace 50% of phenol in weight- and molar-based, respectively, and then compared with neat PF resin in terms of free formaldehyde content, gel time, pH of the resin, solid content, bond strength and thermal stability. Results showed that BPF-M resin had less free formaldehyde content and longer gel time than BPF-W resin. No significant difference in pH and solid content was observed between bio-oil-based PF resins. Moreover, molar-based substitution resulted in a resin with higher bonding strength than that of weight-based substitution, and both BPF-W and BPF-M showed higher bonding strength then neat PF resin. TGA analysis of the resin revealed that substitution of phenol with bio-oil lowered the thermal stability of bio-oil derived PF resins. However, molar-based substitution of phenol with bio-oil could enhance the thermal stability.

Keywords:

• Bio-oil
• lignin
• phenol formaldehyde
• sustainable

Funding

This work was supported by the Agriculture and Food Research Initiative – “Hydrophobic Bio-Oil-Epoxy Binders for Wood Composites” (Project Award Number 2017-67021-26134), and also “Formation of phenolic resin based interpenetrating polymer network from pyrolysis oils” (Project Award Number 2015-67021-22842). The Auburn University Intramural Grants Program (Auburn, AL, United States) is recognized for startup funding for part of this project. Another part was supplied by National Science Foundation (NSF) Auburn IGERT: Integrated Biorefining for Sustainable Production of Fuels and Chemicals (NSF Award #: 1069004, Auburn University, Auburn, AL, United States). This work was also supported by the Agriculture and Food Research Initiative (AFRI) CAP – ‘‘Southeast Partnership for Integrated Biomass Supply Systems” (Project #: TEN02010-05061). Further, Regions Bank provided partial support and the Forest Products Development Center is acknowledged for supplementary funding of materials and supplies.

Disclosure statement

No potential conflict of interest was reported by the authors.