Investigating The Properties Of Small Diameter Salix Discolor And Its Medium Density Fiberboard

Salix discolor-willow hybrids-as a fast-growing species breed in China, is extensively planted for its characteristics of short growth cycle and high survival rate of transplant. To balance between demand and supply of timber in China, the feasibility of Salix discolor being used as raw material in medium density fiberboard(MDF) was investigated. The fiber morphology, chemical composition, and fiber separation quality of 3-year-old Salix discolor were characterized at first in this paper. And then the bonding mechanism of urea-formaldehyde(UF) and soy protein resin-based Salix discolor MDF was studied. Comparatively analyze the the effects of the raw materials, resin type, and bark on the properties of MDF made from Salix discolor, UF resin and soy protein resin, respectively. Therefore, to optimize the appropriate process parameters of Salix discolor MDF.Fiber quality evaluation and wettability of Salix Discolor results indicated that the content of course fiber, medium-length fiber and short-length fiber were 13.3%, 58.4% and 28.3%, respectively,the fiber packing density of salix discolor is 31.0 kg/m3. The results of electron spin resonance(ESR), static contact angle, and FTIR showed that the amount of free radical on fiber surface increased after grinding, resulting in the better wettability, while the amount of free radical on fiber surface in MDF reduced. It can be concluded that chemical reaction between wood fiber and UF occured during manufacturing process. With certain amount of curing agent, the chemical reaction happens faster with the improved reactivity. UF resin and soy protein resin can bond Salix Discolor well theoretically. Optimizational parameters are deprived by analyzing properties of MDF made from Salix Discolor.The board density of MDF made with Salix discolor affected its physical and mechanical properties significantly. Internal bond(IB), modulus of elasticity(MOE) and modulus of rupture(MOR) increased with the increasing of density, while thickness swelling(TS) after 24 hours decreased. When density is ≥0.75g/cm3, physical and mechanical properties of unpeeled Salix discolor with resin content of 12% can meet the demand of national standards. When resin content increased, physical properties increased as a result.Comparing the influence of different raw materials, resin content, bark content, the results indicate that, MDF made of small diameter log showed the better mechanical properties than that of Salix discolor branches. UF presented the higer bonding strength than soy protein resin, but not significantly. Peeled Salix discolor showed better with respect to physical properties than unpeeled Salix discolor. Based on the obtained results, Salix discolor was proven to be the potential raw materials for medium density fiberboard.