纤维板断面密度分布热压形成过程的研究

Fiberboard VDP forming progress in hot-pressing process.

为优化热压工艺、提高板材质量,该文通过改变两段式热压(高压—低压)工艺各段压力及其对应时间,采用平压法热压不同断面密度分布(VDP)的纤维板,监测热压过程中板坯温度和厚度的实时变化,分析板材VDP热压形成过程以及不同热压工艺对板材VDP的影响。结果表明:热压过程中板坯VDP存在动态变化,内部温度以及热压工艺决定这一动态过程;温度梯度的产生及实时变化是产生板材VDP的重要原因;增大高压压力有助于表层密度的提高;提高低压压力有助于心层密度及心层厚度的增大;表层厚度随着高压保压时间延长而增大;表层到心层的密度梯度随着高压降至低压时间的增加而降低。

Studying the vertical density profile （VDP） forming progress of fiberboard helps understand and improve the hot-pressing technology. The presented work aims to investigate the temperature and thickness changes in real time by changing different pressure and corresponding time in the two stages hot-pressing technology （hot pressure and low pressure）. In doing so, it was hoped to study the VDP forming progress and also the effects of different hot-pressing curves on VDP. The results indicated that there was a dynamic change on VDP and it was determined by the mat inner temperature as well as hot-pressing curve. The existence and changes in temperature gradient were attributed to the important cause of forming the VDP. Increasing the ＂high pressure＂ value would increase the density peak of surface layer; raising the ＂low pressure＂ value would increase inner layer density as well as its thickness; the surface layer thickness would increase along with the extending of ＂high pressure＂ time; the surface-inner density gradient would decrease as time extending from high pressure to low pressure.