木质人造板吸水过程中内部单元体尺寸及相对位置的变化

摘要

吸水易导致木质人造板物理力学性能的变化.为探讨木质人造板吸水后内部单元体尺寸及相对位置的变化,使用X射线断层扫描仪检测吸水前后4种中密度纤维板(MDF)、2种定向刨花板(OSB)和1种胶合板(PW)的内部单元体尺寸及相对位置的变化,分析了吸水导致人造板内部单元体尺寸及相对位置变化的原因,深入剖析了胶黏剂、添加剂和组坯方式对人造板结构稳定性的影响.结果表明,人造板吸水后尺寸增加主要集中在厚度方向.三聚氰胺改性脲醛树脂胶黏剂和石蜡添加剂,二苯基甲烷二异氰酸酯胶黏剂能有效保持MDF内部单元体间相对位置的稳定.吸水后,酚醛树脂胶黏剂所制OSB易发生胶层分离.PW的内部组成结构可更好地保持人造板的尺寸稳定性和结构完整.试验结果为优化人造板生产工艺和指导人造板的合理使用提供了理论依据.%Wood-based panels have been widely used as basic decorative products and construction materials for dec-ades. They play an increasing important role due to the multiple advantages, such as raw material compatibility, ease of implementation, adaptability to continuous processing and standardization of the products. Physical properties of wood-based panels are prone to be influenced by water uptake, which limits the application field of wood-based pan-els. Generally speaking, the water uptake could lead to dimensional instability and decrease in mechanical strength of wood-based panels. Understanding the variation of internal unit during the water uptake process, therefore, is essential for optimizing the production and application of wood-based panels. In order to investigate the size and relative posi-tion of the internal unit changes induced from the water uptake, specimens prepared from four types of medium densi-ty fiberboard ( MDF) , two types of oriented strand board ( OSB) and one type of plywood ( PW) were scanned be-fore and after the water uptake process by using an X-ray CT scanner. The reasons of size and relative position changes caused by the water uptake in wood-based panels were studied. The influence of glue, additives and the way of mat-tress on the structural changes of wood-based panels was discussed during the water uptake. The results showed that the X-ray CT scanning could timely visualize the 3D internal structure of wood-based panels. The dimensional increase in wood-based panels after the water uptake mainly occurred in the thickness direction. The application of melamine modified urea formaldehyde ( MUF) resin, paraffin emulsion and methane-diisocyanate ( MDI) resin could improve the stability of internal structure of the MDF. The glue line detachment in phenol-formaldehyde ( PF) glue line was prone to occur in OSB after the water uptake. The way of mattress in the PW could better stabilize the dimension and internal structure of wood-based panels during the water uptake. The results obtained from this study can be used in optimizing the processing technology and application approaches of wood-based panels.