The Research On Hot-Pressing Process And Performance Of Reconstituted Square Lumber Of Mulberry Branches

In this paper, mulberry branches as raw materials and P-MDI as adhesive, mulberry branches reconstituted square lumber were fabricated using hot-pressing technology in order to seek new substituted resources of wood and ease the status of the shortage of timber supply and demand in our country. Using single-factor and orthogonal test and basing on GB/T 17657-2013, mulberry branches reconsolidated square lumber was measured main performance and analyzed variance results. The paper mainly studied the effect of glue consumption, density, hot-pressing time and hot-pressing temperature on the physical and mechanical properties of mulberry branches reconstituted square lumber, and determined the optimum parameters; Regularities of density distribution of width, thickness and length direction was measured by DENSE-LAB X; Through the wet process, determining the hygro-expansivity rate and drying shrinkage rate of mulberry branches reconstituted square lumber, the dimensional stability of mulberry branches reconstituted square lumber was systematically analyzed. The experiment is an important foundation for further development of reconstituted square lumber of mulberry branches.The main conclusions are as follows:(1) Under the condition of test, the best parameters of mulberry branches reconstituted square lumber are 10%(glue), 160℃(temperature), 45min(time)and the choice of density according to use occasion.(2) Density is very significant factor influencing the performances of reconstituted square lumber of mulberry branches. If density is 0.6 g/cm3, the MOE 9.2GPa, the MOR 90.7MPa, the IB 1.12 MPa and the TS2 h 2.2% will be far greater than LY/T 1580-2010 OSB/2(The requirements of the bearing plate in dry condition) thickness less than 10mm(MOE≥3.5GPa、MOR≥22.0MPa �'� IB≥0.34MPa); Glue greatly influents the IB of mulberry branches reconstituted square lumber, and significantly influents the MOE, MOR and TS2 h of mulberry branches reconstituted square lumber; Hot-pressing time greatly influents the TS2 h of mulberry branches reconstituted square lumber, and has no significant influence on the MOE, MOR and IB; The temperature of four-side pressing machine has excessively important influence on the MOR of mulberry branches reconstituted square lumber, significantly influents the TS2 h of mulberry branches reconstituted square lumber and slightly affects its MOE and IB.(3) Under the condition of test, about density distribution of reconstituted square lumber of mulberry branches, the type is steep and flat in the width direction, steep in the thickness direction and uniform in the length direction. The top surface of density of reconstituted square lumber of mulberry branches is less than the opposite side. Its back surface of density is greater than the front side. With the increase of density, surface high density growth rate is less than the core layer low density growth rate; When the density of mulberry branches reconstituted square lumber is 0.6 g/cm3, the cross section void ratio is large, compression ratio is small and the density value is volatile.(4) When the relative humidity changes, the size of mulberry branches reconstituted square lumber varies. Within the scope of the test, the drying shrinkage and hygro-expansivity of mulberry branches reconstituted square lumber show strong directivity; Mulberry branches reconstituted square lumber hygro-expansivity ratio and dry shrinkage of thickness direction are less than its width direction.(5) There is hygroscopic hysteresis phenomenon in mulberry branches reconstituted square lumber. In the process of wet processing, mulberry branches reconstituted square lumber of hygro-expansivity ratio of thickness and width is lesser. D values of mulberry branches reconstituted square lumber was less than 1.5.