| Cornstalk enzymatic hydrolysis residues （EHL） were modified by phase-separationtreatment with p-cresol and sulfuric acid. Then lignin and lignocresol were used to synthesizeepoxy resin. The properties of lignin-based epoxy resin and lignocresol-based epoxy resin werecompared in this study. The main results were as follows:The optimum conditions of lignin phenolation which based on the results of single factorand orthogonal tests were as follows: Suitable concentration of sulfuric acid for EHL was60%,reaction time was60min, reaction temperature50oC, dosage of sulfuric acid was10mL/g. Theyield of obtained lignocresol was52.62%（based on its Klason lignin）, and the molecular weightof lignocresol was2933. The structure of lignocresol was characterized with FT-IR, UV,1H-NMR and GPC. The obtained results indicated that the content of phenolic hydroxy group canbe improved efficiently and the molecular weight was dramatically decreased. It was concludedthat the thermo stability of lignocresol decreased compared with EHL.The optimum conditions of synthesize epoxy resin which based on the results of singlefactor were as follows: the molar ratio of epoxy chloropropane to hydroxyl group was10:1,molar ratio of NaOH to hydroxyl group was1.2:1, reaction time3h, reaction temperature80oC.In this condition, the epoxy values of lignocresol-based epoxy resin and lignin-based epoxy resinwere0.151mol/100g and0.078mol/100g, respectively. In FT-IR spectrum of lignin andlignocresol-based epoxy resin, the910cm-1 absorption peak derived from the epoxy group,indicating that epoxy groups connect up to lignin successfully. The properties of curing blends oflignocresol-based epoxy resin and E44resin were characterized with TG, DSC, tensile strengthand breaking elongation. The thermo stability of lignocresol-based epoxy resin increased incomparison with the lignin-based epoxy resin. Td of curing blends slightly decreased withincreasing content of lignocresol-based epoxy resin. However, the decrease in Tdwas small,indicating that the thermal stability of curing blends was not affected by the introduction oflignocresol molecules into the epoxy resin. Tg increased with increasing lignocresol-based epoxyresin contents in the curing blends. The tensile strength of curing blends, with20%content oflignocresol-based epoxy resin, was109%higher than that of E44resin. The breaking elongationof curing blends, with20%content of lignocresol-based epoxy resin, was58%higher than that ofE44resin. It was concluded that the additive amount of lignin in epoxy resin was efficientlyincreased by lignin phenolation. |
PDF Full Text Request