MDI低密度纤维板制备工艺和性能研究

目的低密度纤维板具有质量轻、吸音降噪等优点，可广泛应用于非结构用途的家具制造、建筑装饰、包装、电器设备等领域。与中密度纤维板相比，低密度纤维板具有力学性能低的缺点，使用“三醛胶”制备的低密度纤维板，力学性能难以达到要求，且甲醛释放量较大。因此，本研究选用胶合强度高、无甲醛释放的异氰酸酯(MDI)为胶黏剂，制备性能较优的MDI低密度纤维板。方法以纤维含水率、细纤维质量分数和热压曲线为工艺参数，通过分析各参数对板材物理力学性能的影响，得出MDI低密度纤维板较优的制备工艺。结果提高纤维含水率，适当延长低压作用时间，可增加表芯层密度比，从而提高静曲强度和弹性模量，但内结合强度略有下降；增加粗纤维的质量分数可有效提高静曲强度和弹性模量，内结合强度降低，吸水厚度膨胀率略有增加。本研究得出的MDI低密度纤维板较优的制备工艺为:纤维含水率16%，热压曲线C，细纤维质量分数60%。通过保温系数和甲醛释放量测定，发现MDI低密度纤维板与同等密度的保温材料相比具有较好的保温性能，甲醛释放量较低。结论本研究中制备的MDI低密度纤维板各项性能均可以满足LY/T 1718—2017《低密度和超低密度纤维板》中干燥状态下使用的家具型低密度纤维板的性能要求，在家具制造、保温建筑材料等领域具有广泛的应用空间。 

Preparation process and properties of MDI low density fiberboard

ObjectiveThe low density fiberboard (LDF) has advantages of light weight, sound absorption and noise reduction, and can be widely used in the fields of furniture manufacturing materials, building decoration materials, packaging materials, electrical equipment materials, etc. Compared with medium density fiberboard, low density fiberboard has disadvantages of poor mechanical properties. Low density fiberboard prepared by melamine resin adhesive, phenolic resin adhesive or urea-formaldehyde resin adhesive is difficult to meet the requirement of the mechanical properties, and its formaldehyde emission is difficult to reach the E₁ standard. Therefore, MDI low-density fiberboard with low density and excellent performance is prepared using isocyanate (MDI) with high bonding strength and formaldehyde-free release as adhesive.MethodIn this study, fiber moisture content, fine fiber ratio and hot pressing curve were taken as process parameters to analyze the influence of various parameters on physical and mechanical properties of LDF, and the optimal preparation process of MDI low density fiberboard was developed.ResultThe results showed that increasing moisture content of fiber and prolonging low-pressure time can increase density ratio of surface layer to core layer, thereby increase MOR and MOE, but IB was slightly decreased; increasing the mass fraction of coarse fiber can improve MOR and MOE effectively, while IB was decreased, TS also increased slightly. The preferred preparation process of MDI low-density fiberboard obtained in this study was: 16% fiber moisture content, hot-press curve C, 60% fine fiber. Through measurement of the thermal insulation coefficient and formaldehyde emission, it was found that MDI low density fiberboard had a better thermal insulation performance than the same density thermal insulation materials, and formaldehyde emission was low.ConclusionMDI low density fiberboard prepared in the study can meet the requirement for furniture LDF under dry condition of Low density fiberboard and ultra-low density fiberboard. So it can be used widely in furniture making and building insulation materials.