Study On Technology And Self-bonding Mechanism Of The Environment Friendly Binderless Particleboard From Kenaf Stalk And Ramie Stalk

With the improvement of economic level and people's living standard, we demand more and more wood. As our country is short of timber resources, contradiction between wood supply and demand is getting more and more obvious, thus saving existing wood, Making full use of the existing forest resources and artificial fast-grow forests, developing replacements of wooden products will be long-term main trend for China's wood industry.Crop-stalk go by the name of secondly forest resource in the world, it is a vital substitute for the industry of wood-based panels. Our country is rich in kenaf and remie stalk resources, is one of the three main kenaf producing countries, accounts for more than90%of world's ramie output. Under the severe shortage of wood supply and demand situation, as a substitute for the production of wood based panels, kenaf and remie stalk will show a considerable economic benefits, social benefits and ecological benefits. Making envioronmental friendly binderless particleboard can not only make full use of idle resources of kenaf and remie stalk, ease the wood supply and demand, solve the the problems of environmental pollution caused by bumning it, but also the panels have no emissions of formaldehyde,which can meet the demand of environmental protection.Under the condition of ordinary hot pressing, with kenaf stalk particle as the raw material, using compound additives, taking hot-pressing temperature, hot pressing time, board density and amount of additive as variable factors, Single-factor experiments were carried out to discuss the influence of the factors on binderless particleboard. We get better panel-making technology parameters:particle moisture content(MC)20%, board density0.7g/cm3, hot-pressing temperature190℃, hot-pressing time7minutes and amount of additive16%. The kenaf stalk binderless particleboard produced under the conditions can meet the requirements of GB/T4897-2003at the aspects of modulus of rupture (MOR), internal bonding strength(IB) and modulus of elasticity(MOE).With ramie stalk particle as the raw material, on the basis of using compound additives, taking hot-pressing temperature, hot pressing time, amount of additive and particle moisture content as variable factors, orthogonal test were carried out to determined the optimum conditions of binderless particleboard. And on that basis, we discussed the influence of board density on the performance of the board. The results showed that the optimum manufacturing parameters of ramie stalk binderless particleboard were as follows: hot-pressing temperature190℃; hot-pressing time7minutes; mat moisture content(MC)25%and amount of additive16%. The kenaf stalk binderless particleboard with density of0.8g/cm3produced under these conditions can meet the requirements of GB/T4897-2003at the aspects of modulus of elasticity (MOE) and internal bonding strength(IB). modulus of rupture (MOR) and thickness swelling (TS) were close to the standard.With the analysis of infrared spectroscopy and X-ray diffraction, the self-bonding mechanism of ramie stalk bindless particleboard was explored. In the infrared spectrum of ramie stalk bindless particleboard produced under hot press condition, the positions and relative absorb intensity of major peaks changed, the intensity of diffraction strongest points and the positions also changed in X-ray diffraction spectrums. The result showed that:self-bonding of binderless particleboard from ramie stalk were mainly caused by using the additive, On the one hand, the additives promoted the degradation of celluloses and hemicelluloses, on the other hand, saccharide in itself also involved in the condensation polymerization, forming the relatively stronger combination. During the hot pressing processa few hemicelluloses and celluloses degradated to furfural compounds under high temperatures, and then occurred condensative reactions with lignins having the structure of phenolic hydroxyl, finally, they formed adhesive compounds which are similar to phenolic resins. Heated under high temperatures, ligins could also occur condensative reactions between themselves to form compounds similar to phenolic resin in a short time, played the role of adhesive. Under the condition of high temperature and pressure, additive and carbohydrate of lignocellulosics turn into insoluble polymer. It formed the reliable interface bond, make binderless particleboard having higher mechanical strength and considerable water repellency.