Study On The Influence Of Manufacturing Process On Properties Of Fibrosis Veneer Scrimber

In recent years,natural forest resources is seriously short,and plantation resources are abundant,so the contradiction between supply and demand of timber resources is outstanding.Through the technology of wood material reconstitution,we can improve the properties of fast-growing wood.It will be an effective way to alleviate the demand for large diameter timber and the dependence on the imported material products by improving the performance of the fast-growing timber and developing the engineering decoration and structural materials with high strength and stable performance.At present,research and production of scrimber in China is still in its infancy.The research focuses on the physical and mechanical properties of scrimber,but the surface and aging resistance of scrimber are relatively few.In this paper,combined with the application direction of current products,scrimber were prepared using poplar and larch as raw materials and phenolic resin as adhesive.The changes of PF resin adhesive in the production process were discussed by using differential scanning calorimeter(DSC),scanning electron microscope(SEM),fourier transform infrared spectrometer(FTIR),and X ray photoelectron spectroscopy(XPS).The effects of factors such as density,impregnation and veneer thickness on mechanical properties,water resistance,surface properties and weathering resistance of scrimber were systematically studied.The following conclusions were drawn:(1)The curing time of adhesives is longer by 118.6%after dipping larch,and the curing time of adhesives is shorter by 29.9%after dipping poplar.After drying,the resin retention activity of6mm thickness veneer is higher,and the weight average molecular weight increased by 113.3%.During the post drying period,after 30 days,the molecular weight of poplar and larch veneer adhesives increased by 314.1%and 291.4%,respectively.After 90 days,the decline of water resistance of the veneer of the boiling water cycle at 100?28h was the largest,and the TS of poplar and larch veneer increased by 35.3%and 54%,respectively.(2)For different tree species,poplar and larch,as the density of the scrimber increased,the TS decreased by 43.86%and 59.24%,respectively,and the static bending strength,elastic modulus,compressive strength and horizontal shear strength of poplar scrimber increased,and above mechanical properties of larch scrimber increased first and then decreased and their turning point was about at 1.15g/cm~3.In manufacturing process factors,density has the most significant influence on mechanical properties and water resistance of scrimber,the second is the impregnation and the thickness of the veneer,pavement method had no significant effect on mechanical properties and water resistance of scrimber.With increasing density,the static bending strength,elastic modulus,compressive strength and horizontal shear strength increased by 32.85%,29.18%,22.65%and 45.6%,respectively,and the TS and WS decreased by 28.56%and 39.84%,respectively.The comprehensive performance of scrimber with density 1.05g/cm~3,impregnation 14%and 6mm veneer was better than others.(3)In the 5 process factors of density,veneer thickness,impregnation quantity,pressing way and pavement method,the most notable influence on hardness and roughness of scrimber was density.With the increase of density,the growth rate of hardness was 106.57%,and the variation range of Ra and Rz was 26.51%and 28.27%respectively.The surface free energy of scrimber increased with the increase of veneer thickness and density.The influence of impregnation amount,pressing way and pavement method on surface free energy was not significant.(4)After 9 months of natural aging,the static bending strength,elastic modulus and horizontal shear strength of scrimber decreased by 15.3%,12.3%and 5.04%,respectively.And the thickness swelling rate(TS)and width swelling rate(WS)increased by 16.98%and 28.37%respectively.After outdoor exposure for 4 months,the L*value,a*value and b*value decreased to a minimum,and the value of?E*ab reached the peak value.The increase of density was beneficial to enhance the color stability of material surface.After 90 days of artificial accelerated aging,the static strength,elastic modulus and horizontal shear strength of scrimber decreased by14.2%,21.8%and 26.8%,respectively,and the TS of scrimber increased by 14.95%and WS decreased by 16.4%.Artificial accelerated aging had no obvious effect on surface roughness.(5)FTIR analysis showed that after natural aging,the stretching vibration of C=C and C-H of lignin characteristic peak decreased,and the hemicelluloses characteristic peak C=O stretching vibration decreased.So,lignin and hemicellulose degraded during natural aging.XPS analysis showed that after aging,the O/C ratio increased,and the relative content of lignin of the scrimber decreased.