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| Abstract |
During hot pressing, we measured continuously the transition of temperature at various positions in the particle board as shown in Fig. 1, made of hammier-mill type particles (splinters) from waste la...uan veneer and soya bean flour as shown in Table 1, with the alumel-cromel thermocouples (diameter 0.3 mm). The hot press cycles were varied and then the physical and the mechanical properties of the board were tested. The results of this study are as follows; 1) The temperature of the outer layer of board raise rapidly at first then slowly approach to the hot platen temperature, but the temperature of the inner layer raise gradually and reach to the maximum value, the lower to the minimum value, and raise again up to the hot platen temperature gradually. Therefore the difference of the temperature between the outer layer and the inner layer of board decrease after passing the minimum value of inner layer temperature of the board. (Fig. 3) 2) The longer the hot press cycle, the higher the value of modulus of elasticity, modulus of rupture and Brinell hardness, but the lower the impact bending absorbed energy of the particles, and the feeding quantity of heat. There is not significant relation between the specific bending strength and the hot press cycle. (Fig's. 4 and 5) 3) The water absorptivity of board is remarkably high at 27 min. hot press cycle, but its value is low at longer than 32 min. cycle and it varys a little as shown in Fig. 6. (This is owing the fact that the quantity of heat feeded is not enough at 27 min. hot press cycle to cure the adhesives in the board.) There is not singificant relationship between the hygroscopicity of board and hot press cycle as shown in Fig. 7. 4) In conclusion; the longer the hot press cycle, the more curing the adhesives, therefore the strength properties except the impact bending absorbed energy, and the water absorptivity are improved, but the more fragile the wood particle, therefore the impact bending absorbed energy decrease contrary.show more
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Export Mendeley
KJ00005470437