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PEER-REVIEWED ARTICLE
Due to the method of chip acquisition, neither their weight as the weight of wood material intended for board production, nor the chips retained on the screens during screening followed a normal distribution of linear dimensions. The linear dimension that was most often characterized by a normal distribution was chip width. Sample histograms of chip width distribution for selected screens are presented in Fig. 1. The results indicated that, for the screening method used in this study, the presence of specific chip sizes on the screen was determined by at least two of their largest linear dimensions. Moreover, the finer the fraction, the more often the linear dimensions followed a normal distribution. However, as shown in Table 3, the differences between the mean and median were usually small (≤ 8%) and concerned mainly the length of the chips. Shape factors, except for slenderness determined for DD and EE chips, were practically the same, regardless of whether they were due to mean or median relationships. AA, BB, and CC chips had similar shape factors. The DD chips had the greatest width coefficient that affected the ease of orientation, and EE chips were characterized by the greatest slenderness. Chip slenderness significantly affected the board bending strength. Linear dimensions of the chips, presented in Table 3, significantly depended on the share of specific fractions in the total weight of the chips.
10 15 20 25 30 35
Size - 5.0 : SW-W = 0.9579; p = 0.0028 Size - 2.5 : SW-W = 0.9861; p = 0.3830
Size - 5.0 Size - 2.5
0 5
0.780 1.116 1.452 1.788 2.124 2.460 2.796 3.132 3.468 3.804 4.140 Distribution of Chips Width [mm]
Fig. 1. Histograms of BB chip width distribution on the screens with 5 mm and 2.5 mm As shown in Table 4, AA, BB, and CC chips were dominated by the fraction retained on the screen with 1 mm mesh. The DD and EE variants contained mainly the chips retained on the screen with 6.3 mm mesh. The share of fine fraction mainly affects the bulk density of the chips, and this parameter determines the shape of the board density profile or internal bond through greater or smaller densities of individual layers. Table 5 shows the mechanical properties of the investigated particle boards. The experimental data indicated that both industrial boards (OSB and MFP) not only met the requirements of relevant standards, but often exceeded them by as much as 100%. The results for the OSB/3 were more favorable. However, of all the investigated boards, MFP was better than OSB as a multi-functional construction board, as MFP also met the requirements of EN 300 (2006) for OSB/3. Moreover, the MFP mean modulus of rigidity was comparable with that of OSB and was accompanied by a very low coefficient of orientation that was 1.14 compared to 2.18 for OSB. The MFP board also had a higher
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Mirski et al . (2016). “Non - strand chips OSB,” B io R esources 11(4), 8344-8354.
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