Study On Steam-injection Hot Pressing Technology Of Bamboo Scrimber

In this paper, researched the steam-injection hot pressing technology of the bamboo scrimber. Analysis the thermal conductivity of bamboo scrimber by thermal conductivity instrument, and the mechanism of heat and mass transfer during hot pressing process was analyzed. Using Fluent to realize the modeling and predicting heat transfer curve of hot pressing process. Design orthogonal experiment to control the process factors such as the time of steam-injection, the density of the mat when inject into steam, the hot pressing time and so on. The modulus of rupture（MOR）, modulus of elasticity（MOE）, moisture content（MC）, density, internal bond strength（IB）, internal bond strength after 2 hours’ water boiled properties of bamboo scrimber were detected. Optimization of the steam-injection hot pressing process of the bamboo scrimber and further guide the industrial production. Using comparative analysis to study the curve of the profile density of the bamboo scrimber and the particle board, which was produced by steam-injection and routine hot pressing. The advantages of high efficiency and good performance of steam-injection hot pressing process were verified. The following conclusions are obtained:1) Through the experiment, the measured thermal conductivity of bamboo scrimber between 0.11w/m?k^-1—0.13w/m?k^-1,and the thermal conductivity of bamboo scrimber with the density and moisture content had a linear positive correlation, specifically,the greater the density of the bamboo scrimber, the greater the thermal conductivity coefficient, the higher the moisture content, the greater the thermal conductivity.2) Through the DSC test of the PF used in the paper, calculated with the peak of DSC curve find that for the 50 mm thickness bamboo scrimber need 4447.5k J to curing. By calculating find that under this condition of steam-injection hot pressing the desired difference temperature of the bamboo scrimber is 94.5℃. In the design verification test, combined with the temperature instrument, the bamboo scrimber need 20 min of steam-injection hot pressing to reach 94.5℃ of difference temperature, the mechanical properties of the bamboo scrimber show that the calculated temperature difference has a certain reference.3) Establish steam-injection hot pressing heat transfer model of bamboo scrimber by Fluent. After the model operation it can be found that the steam-injection hot pressing is basically consistent with the actual test results and of the same trend. The heat transfer model can accurate the internal temperature changes with time of the mat during steam-injection hot pressing with high reliability and also this model can be used to analyze and predict the actual heat transfer process within the mat.4) After the orthogonal experiment and analysis I found that to the dimension of 1100mm×500mm, thickness of 50 mm, density of 0.9g/cm³ bamboo scrimber, the optimal parameters are follows: hot pressing temperature is 170℃, hot pressing pressure is 4.7MPa, steam-injection time is 55 s, the density of the mat when sprayed into steam is 0.5g/cm³, hot pressing time is 18 min.5) The density distribution of the steam-injection hot pressing bamboo scrimber is more balanced than that of the routine hot pressing. The vertical density profile（VDP） curve of bamboo scrimber made by steam-injection hot pressing is smooth, and the density distribution of each layer is average. However, the VDP curve of bamboo scrimber made by routine hot pressing bamboo VDP curve conventional hot pressing is obvious fluctuation, and the difference between the surface layer and the core layer density is large.6) Bamboo scrimber made by steam-injection hot pressing show better physical properties than those made by routine hot pressing. The more differences of vertical profile density will make the VDP curve more steep. Because of the density difference between core and surface layer became larger, the modulus of rupture and modulus of elasticity become greater, internal bond strength become smaller, edge grip nail force decreases. Steam-injection hot pressing heat equalization which make the density difference between core and surface layer very small and the VDP curve smooth.