玉米秸秆皮单板层积材制备工艺优化

Manufacturing technology optimization of laminated veneer lumber from intact corn stalk rinds

为将组分分离后的完整玉米秸秆皮用于人造板生产,该文以去除表皮层后的完整玉米秸秆皮为原料,以异氰酸酯胶为胶黏剂进行了玉米秸秆皮层积材的制备试验,并分析取样高度、施胶量、热压温度、热压时间等工艺条件对玉米秸秆皮层积材物理力学性能的影响。结果表明,利用穗位部及根部位置玉米秸秆皮制备的板材的性能,除内结合强度较小外,其他性能优于穗位部以上位置玉米秸秆皮制备的板材(P<0.01);随着施胶量的增大,静曲强度、弹性模量、内结合强度等力学性能显著增大(P<0.01),其吸水厚度膨胀率和吸水率都呈减小趋势;在热压温度为150℃、热压时间为6 min时,玉米秸秆皮层积材的力学性能较好,但随着热压时间的增大,其吸水厚度膨胀率和吸水率都增大。在取样高度为玉米秸秆的根部、施胶量为12%、热压温度为150℃、热压时间为6 min最优工艺试验条件下,玉米秸秆皮层积材达到了GB/T20241-2006《单板层积材》、LY/T1611-2003《地板基材用纤维板》的使用要求。该研究为玉米秸秆皮材料化利用及其制板工艺优化提供了理论基础与技术依据。

The utilization of agro-residues as a kind of raw material for making composite board is beneficial to boom rural economy, protect forest and construct ecological agriculture. Corn stalk rind separated by the rind-pith-leaf separation equipment, as the major component of corn stalk, can be used as raw material for producing composite board because of its high mechanical strength. The intact corn stalk rinds after the removal of the epidermis in different heights and the polymeric diphenylmethane isocyanate（p MDI） were used as the material, and the composite boards from the intact corn stalk rinds were produced by a new technology for the laminated veneer lumbers（LVL） in this study. The influences of the sampling height, the mass fraction of adhesive, the hot-pressing temperature, and the hot-pressing time on the physical and mechanical properties of the LVL were investigated. The following physical and mechanical properties were measured according to GB/T17657-2013： modulus of rupture, modulus of elasticity, internal bond strength, thickness swelling in 2hours, and water absorption in 2 hours. The results showed that the mechanical properties of the LVL at the root and the ear part were better than those at the top part except the IB; with an increase of the mass fraction of adhesive, the mechanical properties of the LVL such as the MOR, the MOE, and the IB increased significantly（P〈0.01）, while the values of physical properties such as the TS2 h and WA2 h were decreased; the mechanical properties of the LVL were better when the hotpressing temperature was 150℃ and the hot-pressing time was 6 min, but the values of physical properties were increased with the hot-pressing time increasing. The optimal parameters for the manufacturing process of LVL from corn stalk rinds were as follows： The sampling height at the root, the adhesive content of 12%, the hot-pressing temperature of 150 ℃, and the hot-pressing time of 6 min. Under the optimized conditions, the MOR, MOE, IB, TS2 h and WA2 h of the LVL were（74.6±1.45） MPa,（6705.5±116.3） MPa,（1.40±0.02） MPa, 6.6%±0.32% and 31.9%±2.09%, respectively. The mechanical and physical properties of the LVL could meet the Chinese national standard requirements for flooring fiberboard belonging to ordinary type and the LVL with the modulus of elasticity of 6 000 MPa. These findings provide theoretical basis and technological support for the board-making process by intact corn stalk rinds and the improvement of physical and mechanical properties of the board.