Research On The Effect Of Wax Emulsion Waterproofing Agent On Medium Density Fiberboard

With the development of forestry processing industry, particularly the rapid development of wood-based panel industry, the production of Medium Density Fiberboard (MDF) has increased dramatically and its application is wider and wider. In addition, the market is demanding higher physical and mechanical properties on the MDF, with focus on the waterproof performance. Two kinds of waterproofing additives– solid wax and melted wax, are widely used in the domestic and oversee MDF industry. However, they are increasingly difficult to meet the requirements of advanced manufacturing process. Using emulsion wax as a waterproofing agent in the MDF production not only can improve the waterproof performance without affecting its strength properties, but also can reduce wax usage and costs. Consequently, solving this problem is highly important to the MDF production enterprises, which also has immense implications in improving the quality of MDF and broadening its application areas.The primary purpose of this study is to examine the application of the emulsion wax in the MDF production and to compare the waterproof performance, mechanical properties and economic benefits associated with MDF using three different waxes as waterproofing agent, including melted wax, reduced melted wax and emulsion wax. Three factors (density, the amount of emulsion wax and glue) and three-level orthogonal analysis are used as a means to explore the impacts of emulsion wax on the thickness of MDF. Some principal conclusions are listed below:1.Comparison experiments were conducted to examine the impacts of reducing the amount of melted wax used in the MDF production on the Thickness Swelling (TS) of MDF. The resulted average TS was 11.12% with reduced amount of melted wax usages, which was fairly higher than that of normal amount of melted wax usage. It is evident that directly reducing the amount of melted wax usage in the MDF production has a relative great influence on TS and could not guarantee the quality of MDF. As a result, lower costs could not be achieved by merely reducing the amount of conventional melted wax usage in the MDF production.2.The results of orthogonal test and range analysis indicated that amongst all the factors affecting the MDF TS, the density was greatest, followed by the glue amount, and the amount of wax usage was least. The better process parameters obtained from the experiments were that the density of 800kg/m3, the amount of adhesive applied to 10 % and emulsion wax amount of 1.0%. Within a certain range, as the amount of emulsion wax and glue and density increased, the TS decreased and the internal bonding strength (IB) increased. However, when the amount of emulsion wax was increased from 1.0% to 1.3%, IB began to decline.3.Using the optimizing process obtained by the orthogonal experiments to produce the MDF with the thickness of 21mm, 15mm, and 6mm, The TS respectively were 5.782%, 7.0285% and 11.307%.As national standards, with the reduce of thicknes of MDF,allow have a high Thickness Swelling .The results showed that using emulsion wax as waterproofing agent for the production of thin, medium, thick three kinds MDF were in line with national standards for MDF and was feasible.4. Compared with the melted wax, emulsion wax has high stability, good fluidity, small particles, good diffusion and homogeneity and has a certain mechanical strength in the wax-water interface making the intensity of interfacial film increase. Therefore, when using the emulsion wax as waterproofing agent to produce MDF, could both reduce the amount of wax and improved the waterproof performance and guaranteed the strength to meet the practical application.5. Using the same amount of emulsion wax as a substitute to melted wax in the MDF production, the costs can be reduced by 15-20%. For example, if 1% of compound emulsion wax was used as waterproofing agent, the costs could be reduced by 13.5 yuan / m3. For a MDF producer with the annual capacity of 50000 m3, the costs saved are around 650000 yuan. Given the total MDF production of 2008 in China, the total costs saved can reach 360 million yuan for one year. As a result, using emulsion wax instead of melted wax as a waterproofing agent in the MDF production can reduce production costs as well as increase economic efficiency.