Preparation and characterization of chemical grouting derived from lignin epoxy resin

Lignin was used herein to prepare chemical grouting materials as replacements for petroleum-based epoxy precursors. Demethylation, phenolation, and hydroxymethylation were conducted and the products were characterized via FT-IR, 1H NMR, and GPC. A quantitative NMR method was used to study the precise changes in the functional group composition. Raw lignin (RL), demethylated lignin (DML), phenolated lignin (PHL), and hydroxymethylated lignin (HML) were respectively reacted with epichlorohydrin to synthesize various lignin epoxy resin (LEP), including raw lignin epoxy resin (RLEP), demethylated lignin epoxy resin (DMLEP), phenolated lignin epoxy resin (PHLEP), and hydroxymethylated lignin epoxy resin (HMLEP). With LEP as feedstocks, new grouting materials were prepared and the effects of the RLEP content and the LEP variants were investigated. The results demonstrated that the prepared lignin epoxy grouting resin had outstanding viscosity and mechanical properties with RLEP content up to 16%, and this performance greatly exceeded the industry standard. DMLEP, PHLEP, and HMLEP were able to provide better tensile properties, heat-resistance, chemical-resistance and curing performance compared with that achieved with RLEP. Overall, lignin has displayed great potential in replacing petroleum-based materials for the preparation of high-performance chemical grouting materials.