Study On The Phenolic Modification Of Enzymatic Hydrolysis Lignin And Its Applications In Lignin-based Polyurethane

The aim of this work is to prepare lignophenol through a phase-separation system composedof p-cresol and sulfuric acid using the materials of enzymatic hydrolysis corncob residues. Theeffect of different factors including sulfuric acid concentration, creaction temperature, creactiontime and the dosage of acid were investigated. Then, single factor and orthogonal experimentalmethod was adopted to obtain the best formula and technique for the phenolation. Then theinfluence of two different synthetize methods on properties on waterborne polyurethane werediscussed. The main work and conclusions are as follows.（1） In the process of phenolation, orthogonal experimental method was adopted to obtain thebest formula and technique for the phenolation. The results showed that the creactiontemperature was the most important determinant and the sulfuric acid concentration took thesecond place. The best technical is: temperature40℃, concentration60%, creaction time60min,dosage of acid20mL/g, yield of lignophenol is53.85%, content of pHOH is1.23mol/C9.（2） Compared to the corncob residues, the FT-IR spectra of lignocresol show bands at815cm^-1,815cm^-1resulted from combined cresols, this indicated this method has good modified effects.（3） The structure of lignocresol was characterized with UV,1H-NMR and GPC. The resultsindicated that the content of phenolic-hydroxy group can be improved efficiently, themolecular weight also be simplified.（4） In the process of mechanical blending modified polyurethane, the tensile strength and thewater resistance of coating film of WPU increased with increasing amount of lignocresol,tensile strength increased from43.5MPa to65.32MPa. The elongation at break decreased withdecreasing as lignocresol content increased. The thermal property was studied by TG analysis,Maximum thermo-grabimetric temperature increased from375℃to415℃，the heat stabilitywas improved as lignocresol content increased.（5） In the process of copolymerization modified polyurethane, tensile strength increased from48.51MPa to64.49MPa. Cross-linkage groups of the water-borne PU are improved, and thewater resistance and mechanical property are better than the waterborne PU beforemodification.（6） Lignophenol from enzymatic hydrolysis corncob residues modified polyurethane was thebest of the three materials.