Study On Process Optimization Of Veneering Plywood Covered With Ultra-thin High Density Fiberboard

On the basis of ordinary plywood,veneered plywood is a kind of veneer paving plate on the upper and lower surfaces of plywood,which makes up for the defect that domestic plywood material is poor and cannot be directly decorated.In order to meet the finishing requirements,each plywood requires 2 poplar veneers(whole sheet),after 2～3 times of molding processing,energy consumption,material consumption,high cost,serious environmental pollution.Therefore,this study innovatively uses high-density fiberboard with a thickness of 1mm to replace expensive veneers to press the plywood to form a high-quality decorative surface layer on the surface of the plywood.Using single factor analysis,response surface optimization,SEM surface micro-morphology analysis,profile density analysis and other methods,the optimization of hot pressing process of secondary forming decorative plywood,the influence of different substrate tree species on the performance of secondary forming decorative plywood,the influence of different fine material density on the performance of primary forming decorative plywood and the comparison of primary forming process and secondary forming process were discussed.Finally,the optimal process was selected.In order to achieve the use of low-quality materials to prepare high-performance decorative plywood products,it provides a certain process reference for the production practice research and development of wood-based panel enterprises.Through experimental research,the following conclusions are drawn:(1)Optimization of hot-pressing process for veneered plywood of secondary molded fiberboard:Hot-pressing temperature has a highly significant effect on the surface bonding strength of veneered plywood,while hot-pressing time and pressure have little effect on it;in terms of impregnation stripping performance,hot pressing temperature and pressure have a significant effect on it,and hot pressing time has a significant effect.In the second interac tion experiment,the interaction term of hot pressing time and hot pressing pressure had a significant effect on the impregnation stripping performance of the sheet,and the interaction of the other interaction terms on the impregnation stripping strength and surface bonding strength was not significant.The optimal hot pressing process obtained by parameter optimization comparison experiment is 150°C,210s and 0.8MPa.(2)Selection of tree species for decorative plywood substrate of secondary molding fiberboard:In terms of appearance quality,poplar substrate has little glue penetration,pine substrate has better appearance quality,and eucalyptus substrate has less bubbling and glue penetration.In terms of surface bonding strength and immersion stripping length,the veneering plywood of poplar substrate was 1.47MPa and 43mm,the veneering plywood of pine substrate was 1.34MPa and 11.5mm,and the veneering plywood of eucalyptus substrate was 1.29MPa and 97mm.Through the comprehensive analysis of appearance quality,surface bonding strength and immersion stripping length,the veneering board with poplar as the substrate has the best performance.(3)The density optimization of one-time forming fine material decorative plywood:when the fine material density is 0.8g/cm~3,the surface bonding strength and immersion stripping length of fine material decorative plywood are 0.98MPa and 16mm;when the density of fine material is 0.9g/cm~3,the surface bonding strength and immersion stripping length of fine material decorated plywood are 1.11MPa and 19mm;when the density of fine material is 1g/cm~3,the surface bonding strength and immersion stripping length of fine material decorated plywood are 1.25MPa and 16mm.When the density of fine material is1.1g/cm~3,the surface bonding strength and the length of dipping and peeling of fine material veneer plywood are 1.33MPa and 88mm.By analyzing the surface bonding strength,immersion stripping length and SEM surface microstructure of the sheet,the performance is better when the fine material density is 1g/cm~3.(4)The comparison of one-step forming fine material veneering plywood process and two-step forming fiberboard veneering plywood process:both of them meet the requirements of national standard GB/T 15104-2006’decorative veneer veneering artificial board’.After twice hot pressing,the bonding between fiberboards and between fiberboards and plywood substrates was closer.The surface bonding strength and dipping peeling length of the board were 1.45MPa and 15mm.The surface bonding strength and dipping peel strength of fine veneer plywood are 1.25MPa and 16mm,and the surface bonding strength and dipping peel strength of the secondary molding process are better.Through the analysis of the surface bonding strength,dip-peeling length and SEM interface of the two,it was found that the surface fiber structure was more compact and the surface was smoother after secondary hot pressing.