  Citation: Asafu-Adjaye, O.A.; Street, J.; Bansode, A.; Auad, M.L.; Peresin, M.S.; Adhikari, S.; Liles, T.; Via, B.K. Fast Pyrolysis Bio-Oil-Based Epoxy as an Adhesive in Oriented Strand Board Production. Polymers 2022, 14, 1244. https://doi.org/10.3390/ polym14061244 Academic Editor: Ralf Schledjewski Received: 31 January 2022 Accepted: 16 March 2022 Published: 19 March 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). polymers Article Fast Pyrolysis Bio-Oil-Based Epoxy as an Adhesive in Oriented Strand Board Production Osei Asibe Asafu-Adjaye 1, *, Jason Street 2 , Archana Bansode 3 , Maria L. Auad 3 , Maria Soledad Peresin 1 , Sushil Adhikari 4 , Terry Liles 5 and Brian K. Via 1 1 School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA; soledad.peresin@auburn.edu (M.S.P.); brianvia@auburn.edu (B.K.V.) 2 Department of Sustainable Bioproducts, Mississippi State University, Starkville, MS 39762, USA; jts118@msstate.edu 3 Department of Chemical Engineering, Auburn University, Auburn, AL 36849, USA; asb0062@auburn.edu (A.B.); mla0001@auburn.edu (M.L.A.) 4 Department of Biosystem Engineering, Auburn University, Auburn, AL 36849, USA; sza0016@auburn.edu 5 Huber Engineering Corporation, Commerce, GA 30530, USA; terry.liles@huber.com * Correspondence: oaa0014@auburn.edu Abstract: The objectives of this study were to utilize bio-oil-based epoxy resin in oriented strand board (OSB) production and investigate the effect of bio-oil substitution in epoxy resin as an adhesive for OSB production. Bio-oil was produced by the fast pyrolysis (FP) process using southern yellow pine (Pinus spp.). Bio-oil-based epoxy resin was synthesized by the modification of epoxy resin with FP bio-oil at various substitution levels. Acetone extraction using a Soxhlet process indicated a superior cured reaction of bio-oil and epoxy resin at 20% bio-oil substitution. FTIR spectra corroborated the Soxhlet extraction with the removal of the epoxide peak signature within the cross-linked polymer. Images from the scanning electron microscopy suggested bulk phase homogeneity. OSB panels were tested according to ASTM D1037-12. The modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength, and water resistance (thickness swell and water absorption) properties of the OSB panels were feasible at bio-oil substitution up to 30% in the epoxy resin system. Keywords: epoxy resin; fast pyrolysis; bio-oil; oriented strand board (OSB) 1. Introduction Lignocellulosic biomass is known to be a suitable replacement for fossil-derived chemicals through thermochemical conversion processes. Biomass sourced chemicals are “green” and could reduce environmental pollution. One of the thermochemical processes which have received a myriad of attention is pyrolysis. Biomass pyrolysis to obtain a liquid fraction known as bio-oil occurs under anoxic conditions at high temperatures (~450–500 ◦ C). When the residence time is at or less than 2 s, the process is called fast pyrolysis [1]. Detailed characterization of fast pyrolysis process and products is well- documented [2–5]. Reactive organic compounds are found in biomass fast pyrolysis (FP) bio-oil, including phenolic monomers and oligomers, furans, carboxylic acids, ketones, etc. [4,6]. In wood composite (e.g., OSB) manufacturing, wood residues from an off-cut could be processed and converted into fast pyrolysis bio-oil to provide energy for heating and chemicals for adhesive synthesis. Oriented strand board (OSB) is engineered with multiple rectangular-like thin-cut wood strands (or flakes), coated with thermoset adhesives and are pressed at a high temperature and pressure. OSB is like plywood in construction in that the core layers are oriented perpendicular to the surface layers. Currently, polymeric diphenylmethane diisocyanate (pMDI) and phenol formaldehyde (PF) adhesives are the major adhesives used in OSB production. pMDI has been used as a core resin and PF as a surface resin Polymers 2022, 14, 1244. https://doi.org/10.3390/polym14061244 https://www.mdpi.com/journal/polymers