Effect of molar ratios of phenol, formaldehyde, and catalyst on the properties of phenol–formaldehyde resin with partial replacement of synthetic phenol with depolymerized lignocellulose biomass

This article presents a method for fractionating and separating phenolic compounds from liquid pyrolysis products of lignocellulosic biomass by a three-stage method, in which up to 30% of phenolic compounds can be extracted. The composition of the phenol-substituting fraction was analyzed by the gas chromatography–mass spectrometry (GCMS) method. The isolated phenolic compounds were used in the synthesis of phenol–formaldehyde resins as a phenol-substituting fraction, with the replacement of 40% of the synthetic phenol in the recipe. Various molar ratios of phenol/formaldehyde and phenol/sodium hydroxide in the resin synthesis recipe were considered, as well as their influence on the strength of the adhesive joint and the proportion of free formaldehyde in the finished modified resin. The results of the studies showed that the optimal molar ratio of phenol/formaldehyde is 1:1.98, with a tensile strength of 1.63 MPa and a free formaldehyde fraction of 0.10% in the resin. The phenol/sodium hydroxide molar ratios considered in this paper did not show an optimal molar ratio, but a tendency to reduce the free formaldehyde content in the resin with a decrease in the introduction of an alkaline catalyst into the resin recipe was revealed, while the strength of the adhesive joint remains normal.