Study On The Variation Law Of Temperature, Air Pressure And Moisture Content Of Flakeboard During Hot-pressing

Compared with regular particle board and plywood, flakeboard has better physico-mechanical properties and price advantage, which is also a board with high performance price ratio .So it is used widely and has vast market. Therefore, it is essential to study its forming mechanism and manufacturing technology.Hot pressing procedure is the key to the flakeboard production. During the process, the physico-mechanical properties of the board are greatly influenced by the distribution of temperature, humidity and pressure in the mat. Thus, in order to thoroughly understand the forming mechanism, establish hot pressing schedule, shorten hot pressing time, and improve the productivity, it is important to study the rule of the heat & mass transfer and explore the relationship between the heat & mass transfer and the properties of board.In this paper, the real-time temperature, pressure and moisture content in the mat are measured consistently and automatically with self-designed test system. Based on the test results and academic analysis, we got the distribution rule and influence-factors of them as well as the relationship among them.The results are as follows:1 The rule of the temperature gradient variation in the mat1) The rule of the temperature gradient variation in the matDuring hot pressing, temperature gradient always exists on the vertical section It is the largest at the beginning and decreases gradually. Unlike the vertical section, the temperature is almost the same over the cross section, and the temperature gradient is quite small, especially for the glued mat. So, the cross section can be viewed as a forisothermal lay. Therefore it was considered that the temperature gradient over the cross sections of the mat is the same.2) From hot pressing experiment results of the glued and unglued mat, it can be known that the influence of adhesives on the temperature distribution of flakeboard can be neglected.3) During hot pressing, the temperature variation of flakeboard can be divided into rapid increasing stage and slow increasing stage. In the two stages, the influence of aim thickness, hot pressing temperature, aim density and moisture content on temperature increasing velocity is different.