Preparations And Characterizations Of Wood-polyurethane Composites With Fast-grown Poplar

After the implementation of Natural Forest Protection Project, fast growing wood has become the main method to solve the contradiction between timber supply and demand. The disadvantages of plantation such as low density and poor processing properties limit its utilization.Based on the previous research of the modification and preparation wood-composite material, the study takes the solid-poplar and the poplar veneer as the main raw materials, chooses different PU resins as the impregnating liquids, make the PU-wood composite. Through comprehensive measuring the WPG (weight percent gain), the Dimensional stability, Mechanical properties, Fire resistance, determine parameters such as impregnating time, impregnating method, impregnating order, curing method and different Catalysts effect on PU/Solid-Poplar material properties. The study adjusts the factors of resin concentration, compression ratio, ventilation time in order to produce the high-performance PU/Poplar-Veneer composite. The thesis also through advanced instrument SEM (Scanning electron microscopy), explains whose influencing factors effect on the physical and mechanical properties of PU/Solid-Poplar material and PU/Poplar-Veneer composite from the changing wood cell structure angle.By the means of SEM, the results indicated that the various morphologies of PU in the wood lead to the different properties of the material. The optimization plan is NCO/OH of PU=3.0, the concentration is 15%, solid-poplar forvacuum treatment, impregnating wood with catalyst and PU respectively, curing the resin by the heating or hot-pressing. This processing will prepare the well-properties materials.Adding 0.9% catalyst species in the process of impregnation, the results indicated that the WPG of each PU/Solid-Poplar material is better than the control, The PU/Solid-Poplar material prepared with diethyltriamine had the best mechanical properties and dimensional stability, The PU resin with N-methyl morpholin, resulted in perfect dimensional stability; however, the mechanical properties had no obvious change.The optimum technological conditions of preparing PU/Poplar-Veneer composite is PU resin concentration is 30%; mole ratio of NCO/OH is 6.0; compression ratio of the composite material is 20%;airing time is 2 hour(under Vacuum time is 1 hour and normal atmosphere pressure time is 1 hour).Wood fire-retardant NH4H2PO4 and AlC13·6H2O solution was used to impregnate poplar veneer, then use those veneers preparing PU/Poplar-Veneer composite. Compared with the control, the WPG of resin and static bending strength are decrease slightly; ASE is increase, but the VSE and MOE change little, show excellent flame retardancy and carbon residue ratio, moreover improve the Resistance Leachability of PU/Poplar-Veneer composite with fire retardant.