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Study on Processes and Self-bonding Mechanism of Binderless Particleboard from Bagasse

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Tutor: XuJianYing
School: Central South University of Forestry Science and Technology
Course: Wood Science and Technology
Keywords: bagasse,additive,bindeerless particleboard,self-bondingmechanism
CLC: TS653.5
Type: Master's thesis
Year:  2013
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With the decreasing of forest resources and the strengthening of environmental awareness of the people, raw materials shortage and free formaldehyde¡¯s problems have become increasing highlights in the development of wood based panel industry. In this study, bagasse was used as raw material for binderless particleboard manufacture by conventional hot-pressing method. During the hot-press, additive A and B as the binder were sprayed onto the particles.The effects of different additive ratio on physical and mechanical properties of binderless particleboard were investigated. The test results showed that ratio of A:B=1:1was best in the selected range. Under ratio of A:B=1:1, pressing time, using additive content, particleboard density, and moisture content of particle as variables, optimum production process was further discussed by single-factor test method. Analysis of variance was used to analysis distinctiveness of impact factors. The test results showed that the optimum manufacturing parameter were as follows:board density0.8g/cm3, additive content10%, hot-pressing time8min, particle moisture content16.7%. After variance analysis of hot pressing process parameters, it was found that board density had a significant impact on physical and mechanical properties of bagasse binderless particle board followed by the influence of additives content. However the influence of hot-pressing time and particle moisture content was not notable.Using additive content and particleboard density as variables, the influence of these two parameters on the dimensional stability of particleboard was discussed. The test results showed that linear expansion (LE), thickness changes (TC) and equilibrium moisture content (EMC) of bagasse binderless particleboard were gradual decreased with additive content and board density improved. The the dimensional stability of particleboard was then increased. Bagasse containing certain amount of sugars, bagasse binderless particleboard is thus easy to mould. Influence of additive content on the anti-mildew of binderless particleboard was investigated. The test results showed that bagasse particleboard without any additives was easy to mould and the anti-mildew ability of binderless particleboard was improved with increasing of additive content.By the analysis of FTIR spectra, X-ray diffraction, thermogravimetric (TG) and differential scanning calorimeter (DSC), the self-bonding mechanism of bagasse binderless particleboard was explored. During the hot-pressed, additive plays two roles. On one hand additive made hydroxy group of cellulose to form hydrogen bonds, thus increasing the bonding strength between the fiber. It also promoted the degradation of hemicellulose. The amorphous was changed and polymerization degree was increased. The the crystallinity was then improved. With the degradation, series of monosaccharide containing Carbonyl were produced. The hydrophobic of Carbonyl improved the water resistance of particlebord. In the DTG curves, acromion was gradually decreased with the increasing additive content at270¡æ. This indicated the change of hemicellulose and lignin composition. On the other hand, chemical reaction has occured between among acids A, carbohydrates from bagasse and additive B, forming insoluble polymer, this increased fiber crystallinity. The polymer formed a solid combination of surface, making particles bond strongly. The mechanical strength of binderless board was reinforced. In the DSC curves, this was expressed the appearance of Endothermic peak at220¡æ.
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