Selection of kraft lignin fractions as a partial substitute for phenol in synthesis of phenolic resins: Structure-property correlation

Jéssica S. Rodrigues*, Amanda de S.M. de Freitas, Cristiane C. Maciel, Sophia F. Mendes, Daryna Diment, Mikhail Balakshin, Vagner R. Botaro

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)


In this work, a strategy was proposed aiming to describe an efficient kraft lignin (KL) fractionation method to extract large amounts of low molar mass lignin to partially replace non-renewable phenol with the KL fractions in the synthesis of phenolic resins. KL from Eucalyptus urograndis wood was refined by a fractionation process in ethyl acetate (EtAc). The lignin-phenol-formaldehyde (LPF) resins were formulated by replacing 25% and 50% of phenol with the fractionated lignin. The lignin employed were KL, fraction of KL insoluble in EtAc (LFIns) and fraction of KL soluble in EtAc (LFSol). The LFSol and LFIns fractions were analyzed for composition, functional group content, and thermal properties. Gel Permeation Chromatography (GPC) results indicated that the lower molar mass lignin fractions (LFSol) showed higher solubility in EtAc. The total hydroxyl groups content (by 31P NMR) of the soluble EtAc fraction increased to 4.73 mmol.g−1 after fractionation. The phenolic resin based on monomers derived from LFSol showed adhesion strength, glass transition temperature and thermal stability with values close to commercial phenolic resins. The better homogeneity of the LPF resin produced from LFSol at 25% phenol substitution resulted in adhesion properties similar to the control resin. On the other hand, LFSol could successfully directly replace 15% of the commercial PF resin (corresponding to > 30% phenol replacement) showing the performance similar to the commercial PF control and significantly higher than the LFIns and non-fractionated KL.

Original languageEnglish
Article number115948
JournalIndustrial Crops and Products
Early online date12 Nov 2022
Publication statusPublished - Jan 2023
MoE publication typeA1 Journal article-refereed


  • Fractionation
  • Kraft lignin
  • OH groups
  • Organic solvents
  • Phenolic resins


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