Study On The Process And Properties Of Producing Panel By Poplar Wood With Hydrothermal Treatment

Dimensional stability and anti-corrosion properties of wood-based panel products have great effects on their applications, and the content reduction of hemicellulose of wood raw material will improve dimensional stability and corrosion resistance of wood-based products. In this paper, the effect of high temperature hydrothermal treatment on the properties of poplar was researched to reduce the hemicellulose content, whose dimensional stability and corrosion resistance improved after being pressed into panels. Variations of mechanical properties, moisture absorption, layer thickness swelling and corrosion resistance of panels made by raw materials treated by high temperature hydrothermal treatment were also studied, the main conclusions of this paper are as follows:(1)Test results of high temperature hydrothermal treating poplar particles test showed that: the poplar particle mass loss rate increased with the increase of treatment temperature and time. The mass loss rate reached 24.9% at a temperature of 170 ℃ and a time of 30 min.HPLC analysis showed that the relative content of hemicellulose of poplar significantly reduced and the relative content of cellulose improved after the treatment. Thermogravimetric analysis showed that hydrothermal treatment improved thermal stability of poplar wood. The surface contact angle analysis showed that initial contact angle of urea formaldehyde glue on poplar became larger, while the balance angle decreased after hydrothermal treatment. Through the calculation of surface free energy changes before and after heat,the results showed that surface free energy of treated poplar increased. Observed by SEM, with the increase of water temperature and treatment time, poplar tissues became loose, thereby increasing the permeability of poplar wood. Infrared spectrum analysis showed that, poplar wood surface functional groups did not essentially change, but differ in content after hydrothermal treatment.(2)The waterproof performance of poplar wood raw material of high temperature hydrothermal treatment for the manufacture of panels had improved significantly. Without water proofing agent, thickness swelling under the condition of 24 h decreased from 23.4% to 13.4%.The mechanical strength of the panels decreased. With the increase of wood raw material mass loss after heat treatment, the static bending strength and internal bond strength of panels decreases gradually. The buried test results showed that after high temperature hydrothermal treatment of the particles and prolonged softening time and hot mill of fiber, weight loss rate of the panels made of above treated materials decreased and corrosion resistance property increased. Waterproof agent comparison test showed that using the optimization process of hot pressed panels saved the amount of water proofing agent in a certain extent.(3)The test results of layer thickness swelling showed that the thickness swelling rate of surface layer of the panel made from high temperature hydrothermal treating poplar particles was larger. The thickness swelling rate of core layer was less, while thickness swelling rate of medium layer was similar to what of overall panels. In the panel made of hydrothermal treated poplar particles, enhancement of hydrophobicity of hydrothermal treated poplar particles prevented moisture penetration into the core layer in a certain extent. In the 24-hour test process of the layer thickness swelling rate, thickness swelling rate of the first 2 hours was large, accounting for a large proportion of the entire thickness swelling rate. The performance testing results of particleboards paved by particles by layer showed that using hydrothermal treated poplar particles as surface layer and untreated poplar particles as core layer to produce paricleboard improved the waterproof performance of the particleboards and made up for the mechanical loss of raw materials after high temperature hydrothermal treatment to some extent. The absorption isotherm line of multiple layer paved particleboard was lower than that of uniform paved particleboards. The linear expansion of particleboards made of poplar raw materials by using high temperature hydrothermal treatment was low.