| 概要 |
The term "juvenile wood " denotes the wood which is made by cambial initial in the growing proccss for 10～15 years after the generation, and therefore, it accounts for more proportion of timber which ...is harvested in the short rotation, and it has been ascertained by Dr.H.WATANABE^<1,2,3)> that the fiber of juvenile wood is shorter than that of mature wood and so on. Accordingly, in this paper, we compared the properties of fiberboard producted from the juvenile wood with that from the mature wood, with a view to investigating on the characteristics of juvenile wood as a material of hard board industry. The test materials were taken from five portions of a 55-year-old SUGI (Cryptomeria japonica D. Don) as shown in Fig. 1, and the qualities of Asplund pulp manufactured from them under a condition as shown in Table 2, were tested. In the next place, the SIS hardboards were manufactured from the nonbeating and sizing Asplund pulp under a hot pressing condition as shown in Table 3, and the properties of board were tested. The following results were obtained from this study; In comparison with the mature wood -pulp and -board, (1) The juvenile wood-pulp was finer and less freeness. (Table 4,7) (2) The juvenile wood-board was inferior in Young's modulus in bending, bending strength, bending stress at proportional limit and absorbed energy in impact bending, but it was superior in Brinell hardness. In water absorption, the juvenile wood-board from heart wood was smaller, in other hand, that from sap wood was larger. (Table 5, 8 and Fig. 2) (3) The yield of juvenile wood-board was less. (Table 5, 8) (4) The differences abovementioned were below 20 %. (Table 6, 9) After all, in the case of the juvenile wood as the material of SIS hardboard, the asplund pulp is finer and worse freeness, the yield of board is less, and the properties of board are relatively harder and more brittle as compared with the mature wood.続きを見る
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