| This research is a part of Public Welfare Program of National Forestry Industry "Preparation technology and demonstration of lignin/PVA compound resins’(20120480306). Take rough wheat straw alkaline lignin as raw material, pretreated by sodium hydroxide solution to prepare wheat straw alkaline lignin. And the wheat straw alkaline lignin/PVA membrane was prepared by wheat straw alkaline lignin and PVA according to the method of physical blending. The microstructure, mechanical properties, oxygen and carbon dioxide transmission, light transmittance, thermal stability and solvent resistance of the membranes were investigated. Then the methylolation of wheat straw alkaline lignin/PVA blend membranes were prepared after the wheat straw alkaline lignin modified by formaldehyde. Besides blend membranes with flame retardant property was prepared by wheat straw alkaline lignin, PVA and FRW. The effect of the addition of wheat straw alkaline lignin and FRW on the mechanical properties, flame retardant properties and thermal stability of the membranes were discussed. And the flame-retardant mechanism of FRW applied to the membranes was provided a preliminary analysis.With the quantity of wheat straw alkaline lignin increasing, tensile strength and elongation at break increased before the mass fraction of wheat straw alkaline lignin reached15%, and then it decreased. And the tensile strength and elongation at break of blend membranes improved37.37%and43.47%, respectively when the degree of polymerization of PVA changed from0588to2488. The transmittance of blend membranes decreased because of the addition of wheat straw alkaline lignin. The barrier performance of the blend membranes increased with the improvement of polymerization degree of PVA. The transmittance of visible light at600nm decreased58.40%,66.21%and83.12%compared with the corresponding PVA membranes, respectively. The solvent resistance of the membranes improved with the increasing of the polymerization degree of PVA and the addition of wheat straw alkaline lignin. The thermal stability of the membranes got improvement because of the addition of the wheat straw alkaline lignin and increased with the improvement of the polymerization degree of PVA.The blend membranes exhited optimal overall properties when the addition of wheat straw alkaline lignin was20%. The tensile strength and elongation at break of blend membranes reached maximum and improved10.1%and14.0%compared with wheat straw alkaline lignin/PVA membranes at the same condition, respectively. The barrier performance of blend membranes got further improvement. The transmission of oxygen and carbon dioxide decreased67.14%and78.46%compared with pure PVA2488membrane,48.20%and64.10%compare to wheat straw alkaline lignin/PVA2488blend membrane. The transmittance of visible light at600nm decreased66.81%compared with wheat straw alkaline lignin/PVA2488blend membrane.Consider mechanical properties and flame retardant properties as evaluation criterion, the results turned out that the tensile strength and elongation at break of wheat straw alkaline lignin/PVA/FRW blend membrane with the optimal overall properties was41.42Mpa and225.38%, respectively. The vertical burning grade rose to V-1compared with wheat straw alkaline lignin/PVA blend membranes. Besides the LOI and carbon yield improved17.04%and77.58%compare to wheat straw alkaline lignin/PVA blend membranes, respectively. And the thermal stability was better than wheat straw alkaline lignin/PVA blend membranes. |
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