| Scrimber is made from wood bundle or fibrotic wood veneer and PF resin,which is compressed and bonded in parallel direction.After more than 40 years of research and development,it has become one of the main ways to utilize the fast-growing wood efficiently.With the use of wood composite materials in the field of wood structure building and wetland landscape facilities,scrimber is gradually used as outdoor exterior materials in outdoor field.Because the water resistance,mechanical properties and corrosion decay resistance are the basic characteristics of outdoor exterior materials,so it is necessary to carry out application research of scrimber.In this paper,the basic characteristics of the poplar and larch fibrotic veneer were studied.Then,the scrimber was prepared by the process factors such as density and resin content,and the mechanical properties,physical properties and surface properties of scrimber were studied.In addition,several analytical techniques such as scanning electron microscopy(SEM),Laser scanning confocal microscope(LSCM),Micro X-ray computed tomography(XCT),fourier transform infrared spectrometer(FTIR),X-ray photoelectron spectrometer(XPS),nanoindentation(NI),transmission electron microscopy(TEM),fourier transformation infrared spectrometer(FT-IR)and X ray diffractometer(XRD)were employed to investigate the the structural evolution,adhesive interface and anticorrosion anti-rot mechanism of scrimber.Several conclusions were drawn from these experiments:1.The physical and mechanical properties of the scrimber can be adjusted through the process parameters,such as density and resin content,to meet the requirements of timber for outdoor use.In terms of water resistance,after 28 h cyclic boiling test,the thickness swelling rate and water absorption of poplar scrimber with the resin content of 18.0% and the density of 1.0 g/cm3 were 23.73% and 34.15%,respectively,which were 54.51% and 46.13% lower than those of the scrimber with the resin content of 8.0% and the density of 1.0 g/cm3,respectively.In terms of mechanical properties,the bending strength and the horizontal shear strength of poplar scrimber with the resin content of 13.0% and the density of 1.15 g/cm3 were 201.37 MPa and 17.99 MPa,respectively,which were 38.71% and 38.49% higher than those of the scrimber with the resin content of 13% and the density of 0.85 g/cm3,respectively.2.When the scrimber was made from the fibrotic wood veneer,the cell structure of the material had undergone a series of structural evolution.From macro perspective,a series of points and line shape cracks occurred on the surface of the fibrotic wood veneer.From the micro perspective,most of the vessels and wood rays and part of the fiber cells of poplar fibrotic veneer were isolated and destroyed,so were part of earlywood tracheids and wood rays of larch fibrotic veneer.These particular cell structures constituted the cell populations of the fibrotic veneer.When the poplar fibrotic veneer was made into scrimber,the rupture of the vessel was compacted and disappeared.The undestroyed vessels,wood rays and fibers were compressed gradually,and the pores of these cells became smaller with the increasing density.The pore diameter and porosity of scrimber with density of 1.15 g/cm3 reached the minimum value,36.5 nm and 17.84%,respectively.3.Firstly,phenolic resin penetrated into the cracks,destroyed vessels,earlywood tracheids and wood rays,and then filled the cavity of these incomplete cells,finally penetrated into the lumen and cell wall of the intact cells.When the poplar fibrotic veneer was made into scrimber,the cured phenolic resin deposited in the cell lumen and cell wall,and the adhesive nail was formed between the cells,which can be used for fixing the incomplete and compressed cells;The distribution of phenolic resin in the cells of scrimber increased with the increase of the resin content.The elastic modulus and hardness of the fiber cell of scrimber were 10.10% and 31.91%,respectively,were higher than those of the untreated wood.4.The corrosion decay resistance of the scrimber can be adjusted by the factors such as density,resin content,and the preservative,so as to meet the requirements of scrimber for outdoor use.After 12 weeks of the erosioninoculation of white rot fungus,the mass loss rate of the poplar scrimber with the density of 1.00 g/cm3 and the resin content of 18.0% was 23.24%,which was 42.77% lower than that of scrimber with the density of 1.00 g/cm3 and the resin content of 8.0%.The mass loss rate of the CuAz treated poplar scrimber with the density of 1.00 g/cm3 and the resin content of 13.0% was less than 10%,reaching the strong high durable corrosion grade level I.These results showed that the CuAz treated scrimber had excellent corrosion rot resistance.The mass loss rate of the larch scrimber with the density of 1.00 g/cm3 and the resin content of 13.0% after white rot and brown rot inoculationerosion was 11.43% and 18.42%,respectively,reaching the corrosion gradedurable level II.5.After 12 weeks of the fungus inoculationerosion,the content of ?-cellulose and hemicellulose decreased,while the content of acid insoluble lignin increased.The greater the resin content and the density and the CuAz treated scrimber,the higher the degree of crystallinity,the smaller the intensity loss of chemical group and the degree of damage to the cell structure.6.The mechanism of corrosion decay resistance of scrimber as shown below:(a)Phenolic resin filled part of the wood cell cavity,and reacted with some active groups of the cell wall to form stable cross-linking;The more the resin content,the more crosslinking groups of the scrimber,thus improving the corrosion resistance of the scrimber effectively.(b)The dense cell structure of scrimber reduced the invasion space and path of the mycelium;The higher the density of the scrimber,the less space between cells,indicating that the increase of the content of fiber and phenolic resin in the unit volume,which inhibited the erosion of decayed fungi effectively.(C)CuAz preservative could penetrate into the vessels,wood rays and fibers,reacted with cell wall to produce copper comple and inhibited the growth and reproduction of fungus,so as to improve the corrosion decay resistance of scimber. |
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