Study On The Gypsum Sawdust Board

The gypsum particleboard is a kind of building material, which takes gypsum as gluing material and takes wood-particle as reinforcing material. It has a long history already. This research's topic is on using the sawdust which is abandoned in the wood industry, instead of the wood particle, as the original material. That can save the wood and recycle discarded products. As a result, it can decrease production cost and increase the economic performance. Meanwhile, the gypsum sawdust board could increase the sorts of gypsum particleboard.As the dimension of the material changing, the wood-gypsum ratio and the water-gypsum ratio was studied. Replacing wood particle by sawdust, the parameter is the wood-gypsum ratio by 0.2 and the water-gypsum ratio by 0.35 in single factor control. Besides, the relationship between the wood-gypsum ratio and the water-gypsum ratio was also explored. The formula,ω= 0.54x+0.28, indicates each water-gypsum ratio has a wood-gypsum ratio to go with it, which should make the board's properties best in the corresponding series together.The temperature effects were explored by analyzing the concentration of Ca²⁺ in the hydrating system and the morphology of gypsum crystals with some modern instruments, such as Fire Atomic Absorption Spectrophotometer (FAAS), Scanning Electron Microscope (SEM) and so on. In addition, the physical and mechanical properties of the gypsum sawdust board was also surveyed. The result shows thatwhen the temperature is 40℃, the gypsum hydration time shortens and the board has higher strength. The application of this condition will shorten the production period and improve the efficiency.The main composition of the gypsum is dihydrate gypsum in the gypsum sawdust board, namely CaSO₄-2H₂O. Through the FTIR diagram's analysis, the cellulose, the half cellulose, the lignin in the wood and the extractives neither combine with the gypsum obviously. So it can be surmised that there is only the physics connections between the gypsum and wood. Therefore, in order to improve the strength of the gypsum sawdust board to satisfy the needs, other chemicals should be joined as the bridge, making the wood and gypsum chemical combination to build up.