二次热压工艺对纤维板性能的影响

Influences of secondary hot-pressing overlaying process on properties of fiberboard

【目的】通过模拟热压贴面工艺,揭示高密度纤维板(HDF)基材在二次热压过程中性能的变化。【方法】控制HDF基材的二次热压工艺条件(热压温度分别为160,180,200和220℃;热压压力为1MPa;热压时间分别设定为30,45和60s),研究热压对HDF板材的厚度、内结合强度(IB)、静曲强度(MOR)、弹性模量(MOE)及24h吸水厚度膨胀率(TS)的影响。根据HDF板材的显微结构,提出了板材中纤维排列的"叠层"和"‘品’字"模型,并结合上述试验,对板材性能变化进行阐释。【结果】经历二次热压后,由于HDF板材受到压缩、内部胶接点受到破坏,板的厚度显著减小(最高压缩率达到8.39%);热压温度越高、时间越长,板材IB、MOR和MOE的降低和TS值的上升越明显。【结论】二次热压工艺对HDF基材性能具有显著影响,建议热压温度不高于180℃、热压压力约1MPa、热压时间小于30s。

【Objective】 This study was conducted to disclose the change of HDF properties during secondary hotpressing.【Method】 Hot-pressing conditions were designed,i.e.,temperature（160,180,200 and 220 ℃）,pressure（1 MPa）,and time（30,45,and 60 s）,to find out the possible changes of HDF properties,including inner bond strength（IB）,bending strength（MOR） and modulus（MOE）,and thickness swelling（TS）.To explain the above changes,two models of fiber orientation in HDF matrix,i.e.,a layering model and a triangle-shaped model,were created,in accordance with the microscopic structure of HDF board.【Result】 HDF boards through hot-pressing were evidently compressed in thickness（with a maximum rate of 8.39%）,and showed lower IB,MOR,MOE,and higher TS values correpondingly at higher temperature and/or with longer pressing time.It was thought that the gluing point between two adjacent fibers was destroyed under secondary hot-pressing.【Conlusion】 HDF could be evidently weakened by secondary hot-pressing process,and it was recommended that hot-pressing temperature be lower than 180 ℃,pressure about 1 MPa,and time shorter than 30 s.