Manufacturing and performance of high density sugi bark boards without synthetic resins, 1: Effects of mat moisture content and hot-pressing schedule on basic properties of the boards
2005
Sekino, N.(Iwate Univ., Morioka (Japan). Faculty of Agriculture) | Sasaki, T. | Taniguchi, H.
A method of manufacturing high density bark boards using sugi (Cryptomeria japonica D. Don) bark particles without adhesive is reported in this paper. Five-millimeter-thick boards with a target density of 1.0 g/cm(3) were fabricated at various mat moisture contents and hot-pressing schedules. The total pressing time and the pressing temperature were fixed at 5 minutes and 180 deg C, respectively, while the hot-pressing schedule that consisted of three pressure steps was mainly changed at the first press pressure from 7 to 9 MPa and subsequent breathing pressure from 0 to 1 MPa. When made with mat moisture contents (MC of 40% or more, the boards showed less variation in modulus of elasticity (MOE) on a board plane as well as an improvement in water resistance due to a great amount of colored area on the board surfaces that may be an evidence of self-bonding. However a breathing pressure of 0 MPa caused rapid eruption of steam, which caused many inner clacks. This resulted in less internal bond (IB) strength and modulus of rupture (MOR). Breathing pressure of more than 0.75 MPa effectively reduced inner clacks, resulting in an improvement in IB strength. Further, the colored area on board surfaces was expanded further by those breathing conditions. When providing a breathing period with some pressure, the best board performance was obtained with a combination of a first pressing pressure of 8 MPa and a breathing pressure of 1.0 MPa (a mat MC of 40%). Similarly, the best board performance was obtained at a combination of a mat MC of 30% and the first pressing step with a pressure of 9 MPa for 80 seconds, even though the breathing pressure was 0 MPa. These boards showed an MOE of 1.9 GPa, an MOR of 12-15 MPa, an IB of 102-121 KPa, and a thickness swelling of 24%-27% by a 24 hour water immersion.
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