The Research On Binderless Ramie Core Particleboard

In the modern world, the forest is decreasing and the timber consumption is increasing. China is a country with large population but lacking forest. Therefore, manufacturing particleboard with ramie core is an effective approach which solves the timber crisis for the moment.Crop-stalk is known as the second of forest resource in the world, it is a vital substitute for the industry of wood-based panels. China accounts for more than 90% of world's ramie output, and ramie has been called "China grass". In china, the high yield and the centralized distribution of ramie have created the condition for the industrialization production. Binderless ramie core particleboard can not only consume a large amount of ramie core residue and solve the problems of environmental pollution of burnning it, but also reduce the formaldehyde emissions. In addition, it can increase the income of peasants at the same time. It has good social, economic and ecological benefits.Based on the previous self-bonding theory, the feasibility of ramie core as particleboard material was investigated from its characteristic and properties of binderless ramie core particleboard in this study.First, the feasibility of ramie core as particleboard material was evaluated from the results of structure, fiber morphology and chemical components of ramie core.Through the orthogonal test and multi-level single-factor test, we discussed the relations between main technical factors and product properties, analyzed the effects of board density, hot pressing time, hot pressing temperature, moisture content of the raw materials, hot pressing pressure,and board thickness on the particleboard properties.The ramie core binderless particleboard with 5mm thickness and density of 0.85g/cm3, produced under the conditions of particle moisture content(MC) 25%, hot-pressing temperature 190℃, pressure 5 MPa and hot-pressing time 7 minutes, can meet the requirements of JIS A 5908 standards at the aspects of modulus of rupture(MOR), internal bonding strength(IB) and thickness swelling rate of water absorption(TS). Compared with other binderless particleboards, ramie core binderless particleboard has high internal bonding strength (0.62MPa).To enhance the performance of ramie core binderless particleboard, three pre-treatment methods (i.e water boiling method, high temperature steaming and steam injection treatment) were conducted on the ramie core. The results showed that high temperature steaming and steam injection treatment could improve the performance of binderless particleboard, but water boiling method would reduce its performance.Another experiment explored the manufacturing technique of self-bonding veneer-overlaid ramie core binderless particleboard. The effects of activating agent amount, hot pressing time and pressing temperature on the particleboard properties were studied. The optimal technical parameters were:board size 200mm×200mm, activating agent amount 30g, hot pressing time 1～1.5min, pressing temperature 160℃. The modulus of rupture of veneer-overlaid particleboard improved significantly.The bonding mechanism of self-bonding particleboard is investigated by analyzing the change of main chemical components of ramie core.Ramie core binderless particleboard is a material which has no formaldehyde and thus causes no harm to environment. It can substitute for some packaging materials or interior decoration materials in current market. It has good social benefits, economic benefits and ecological benefits.