Replacing 100% of phenol in phenolic adhesive formulations with lignin

Lignin, produced as a byproduct of pulp and paper and bioethanol industries, is a polyphenolic compound that has excellent potential to be used as phenol replacement in phenolic adhesive formulation. In this study, the phenol portion of phenol formaldehyde (PF) resin has been replaced by an agricultural-based lignin, which was produced as a byproduct of a cellulosic bioethanol process through dilute-acid pretreatment and enzymatic hydrolysis from corn stover. The PF resol resin was formulated using isolated lignin under alkaline condition. Chemical, physical, and thermal properties of the isolated lignin, PF resin and adhesive were measured using advanced analytical techniques such as Fourier transformed infrared spectroscopy (FTIR), size exclusion chromatography (SEC), phosphorous nuclear magnetic resonance spectroscopy ((31) P NMR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The developed 100% lignin-based adhesive and a commercially formulated phenol resorcinol formaldehyde (PRF, as reference) were used to prepare single-lap-joint samples for mechanical testing. The plywood samples were pressed under exactly the same conditions (time, temperature, and pressure) as what recommended for the commercial PRF formulation. According to two-way ANOVA results, statistically there was no significant difference between the shear strengths of plywood samples made with 100% lignin-based adhesive and those made with the commercial PRF resin. (C) 2017 Wiley Periodicals, Inc.