| The separation of ethanol lignin from washing liquors of whcat straw acid-catalytic ethanol pretreatment has been studied and the optimum separation parameters were attained. Then,the chemical composition of ethanol lignin under the condition was determined. Further more,the configuration transformation and thermal properties were investigated using FT-IR,GPC,~1H-NMR,DSC and TGA.Finally,the ethanol lignin-based polyurethane was prepared from ethanol lignin by solution casting with polyethylene glycol(PEG) and toluene-2,4-diisocyanate(TDI) in the solvent of.tetrahydrofaran(THF).The influences of NCO/OH ratio,ethanol lignin content and PEG molecular weight to polyurethane properties were studied.In addition,Ethanol lignin-based polyethylene under the optimum condition was analysed by FT-IR and TGA.The results of the research are as follows:(1) The optimum separation parameters were:two-stage washing,washing liquid/solid ratio 8mL/100g dried material,temperature 25℃,pH 3.0,washing liquor dilution ratio 2.Under the condition,the recovery of ethanol lignin was 8.98 g/100g dried material.(2) The glass transition temperature of ethanol lignin with high purity was 114.32℃and the temperature with weight loss of 5%was 228.33℃. (3) Syringyl and p-hydroxyphenyl propane units were easier to remove than guaiacyl propane unit in wheat straw acid-catalytic ethanol pretreatment process.(4) Compared with milled wood lignin,ethanol lignin had more unconjugated carbonyl groups and phenolic hydroxyl groups,less methoxyl groups and aliphatic hydroxyl groups,lower molecular weight and narrower molecular weight distributions.(5) Ethanol lignin-based polyurethane had higer tensile strength,more elongation at break and lower water absorption under the condition of NCO/OH ratios 2,20%ethanol lignin content and PEG1000.(6) IR and TGA analysis indicated that ethanol lignin had reacted with TDI and its addition improved the thermal stability of polyurethane.
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