Study On Processes Of Self-bonding Composites

The object of the research is to achieve breakthrough development in the production of self-bonding fiberboard with wood and rice straw materials based on the previous self-bonding theory. The key is to improve the performances of self-bonding board and simplify the processing procedures. The self-bonding wood-based fiberboard can be produced in the conventional middle density fiberboard (MDF) product-line (only removal of glue-made equipments). Two different process methods are applied on the production of self-bonding fiberboard. Method I, to produce 8mm board with density of 0.85g/cm3 under the conditions of active agent 0.7%, blank board with 21% moisture content(MC), hot-pressing temperature 180癈, pressure 3.5MPa and hot-pressing time 12 minutes. The performance of products can reach 2-level of GB of category A particleboard. Method II ,to produce 6mm board with density of 0.85g/cm3 under the conditions of blank board with 21% MC, water repellent agent 1.00%, hot-pressing temperature 180"C, pressure 3.5MPa and pressing time 12minutes. The performance of products can reach 2-level of GB of category 80 MDF.The self-bonding rice straw board with 6mm thickness and density of l.OOg/cm3, produced under the conditions of active agent 2.0% by weight, blank board 19% MC, hot-pressing time 7.0 minutes and the close rate of presser 0.9mm/s, can meet the utilizing performances at the aspects of modulus of rupture, modulus of elasticity and waterproof, but low interior bonding strength (0.135MPa). It's difficult to bond because of thin rice straw fibers with high content of soluble materials and slice. To improve the performances, the rice straw must be made into fibers.The research results on relationship between processing parameters and performances of self-bonding wood-based fiberboard and self-bonding rice straw particleboard show that active agent is mainly effective factor for Method I of self-bonding wood-based fiberboard, the next one is blank board MC; hot-pressing time effects mainly on product performances for Method II. Active agent is mainly effective factor and hot-pressing time and close rate of presser is secondary for self-bonding rice-straw particleboard.The exploring experiments are conducted on self-bonding bamboo particleboard, self-bonding bamboo-wood fiber composite, self-bonding rice straw-wood fiber composite and wheat straw-wood fiber composite. The data show that self-bonding bamboo particleboard can develops required performances when active agent content reaches 0.5%.Poor release of air and product performances can be improved when bamboo particle, rice straw particle and wheat straw particle compound with wood fiber at the rate of 7:3 by weight respectively.With the method of detecting contacting angle between glue liquid and solid surface, wetting property is investigated for self-bonding wood -based fiberboard. Data indicate thatwetting property of self-bonding fiberboard is better than MDF, that wetting property of sanded surface of self-bonding fiberboard made with Method I is inferior to that of unsanded fiberboard, but opposite results to the comparison between sanded surface of self-bonding fiberboard made with Method II and unsanded surface, and that self-bonding fiberboard without waterproof agent has better wetting property than that with waterproof agent.The bonding mechanism of self-bonding fiberboard is investigated by chemical analyses to analyze the main components' changes of wood fiber. The results by FTIR, ESCA, X radial diffraction prove that the change happens for wood fiber on the functional groups and crystal degree of cellulose during the processing duration.