Main Performance Assessment And Application Of Biomass Reconstituted Square Lumber

Biomass resources are a kind of renewable resources, the comprehensive exploitation and utilization becomes priority themes of national medium and long-term development. The contradiction between supply and demand of timber is growing with the shortage of forest resources in our country. The man-made board materials made from farming and forestry surplus have been paid more and more attention. It is an effective way to alleviate the situation of shortage of wood resources, which also provides technical evidences for the high value-added utilization for farming and forestry surplus.Reconstituted square lumber was manufactured based on cotton stalk and mulberry branch. According to the standards of physical and mechanical properties of wood, the effect of density on mechanical properties of reconstituted square lumber made from cotton stalk and mulberry branch with phenolic resin adhesive(PF) and Isocyanate adhesive(MDI) was investigated by single factor test. Mechanical processing items and clear painting properties were studied in this paper referred to the standard of American society for testing and materials(ASTM D1666-87) and the stand of national film adhesion. Various machining defects were classified on the basis of a series of experimental results. Finally, the preliminary exploration of application of reconstituted square lumber was made, which was beneficial fully recognize and exploit the application potential of that. The results also had significance for optimizing the properties of biomass reconstituted square lumber and improving its processing and utilizing levels. The main conclusions were as follows:(1) Density had a significant impact on main mechanical properties of reconstituted square lumber made from made from cotton stalk and mulberry branch with PF and MDI during the range of experiment. The result showed that modulus of elasticity, bending strength and compressive strength increased with the increase of density. When the density was 0.8g/cm3, the mechanical properties of reconstituted square lumber made from mulberry branch was higher than that of reconstituted square lumber made from cotton stalk, the mechanical properties of reconstituted square lumber with MDI(8% resin content)was higher than that with PF(10% resin content).Coefficient of variability of mechanical properties of the two kinds of reconstituted square lumber of different densities and adhesives were blow 10%.(2) In the individual machining test, the quality grades of machining properties of reconstituted square lumber made from cotton stalk were excellent in the items of sanding, boring and shaping, according to the weighted integration method, the quality grade values of the three items were 4.37、4.43 and 4.37, respectively. The quality grades of the machining properties of planning, mortising and turning were good, the quality grade values were 3.47、3.87 and 3.07, respectively. The quality of cross cutting was poorer than others, which was in the middle grade and the quality grade value was 2.63. The quality grade values of machining properties of reconstituted square lumber made from mulberry branch were 4.70 and 4.43 for boring and shaping, which were located in excellent grade. Sanding and shaping were in good grade, planning and turning were in the middle grade, cross cutting was in poor grade. The quality grade value of boring of OSB was excellent, which was 4.33. Planning, mortising and planning、shaping、cross cutting were in good grade and poor grade, respectively.(3) Reconstituted square lumber made from cotton stalk scored 39.5 out of 50 in the comprehensive evaluation score of machining properties, reconstituted square lumber made from mulberry branch and OSB was second and the worst, respectively.(4) The main demerits in the planning were chipped grain and torn grain; the main demerits in the sanding were surface fuzzy and fuzzy grain; the main demerits in the shaping were fuzzy grain and other defects around knots; the main demerits in the mortising, boring, cross cutting and turning were fuzzy grain and torn fiber of different degree.(5) The painting film adhesion of reconstituted square lumber made from cotton stalk and mulberry branch were all above 2 level after painting with nitrocellulose transparent primer and polyester transparent primer. The painting film adhesion increased at first and then decreased with a decreasing surface roughness. The painting film adhesion of reconstituted square lumber reached 1 level after sanding with 240#、320#、360# sand papers with nitrocellulose transparent primer and sanding with 240#、320# sand papers with polyester transparent primer.The change of painting chromaticity of the reconstituted square lumber was a gradual process after painting with two kinds of transparent primer 3 times. The first time painting had the most significant impact on painting chromaticity. The effect on L* and a* of reconstituted square lumber made from cotton stalk was greater than that of reconstituted square lumber made from mulberry branch, while effect on b* was less than that of reconstituted square lumber made from mulberry branch. Lightness difference and chroma difference painting with polyester transparent primer were all higher than that painting with nitrocellulose transparent primer.Glossiness improved significantly after painting with two types of primer, and GZLwas higher than GZT. The glossiness painting with polyester transparent primer was higher than that painting with nitrocellulose transparent primer. Glossiness difference almost disappeared between parallel and vertical to the fiber bundle direction after 3 times painting with two types of primer.(6) A hallstand was designed and manufactured with a solid mortise and tenon joint structure and adhesive nail structure according to the dimension of the reconstituted square lumber, the unique patterns of that achieved good visual effects.