Development of vertically oriented fiberboard I. Manufacture of fiberboards and analysis of fiber orientation

Since the pressing direction in mat forming usually will coincide with the thickness direction of fiberboard, the fibers are oriented parallel to the board plane. That is to say, pressed fibers are oriented normal to the pressing direction. It is expected that five types of oriented fiberboard could be manufactured by changing the direction of pressing the fiber mat, namely, platen-pressed fiber-board, horizontally oriented fiberboard, 3-dimensionally random fiberboard, extruded fiberboard and vertically oriented fiberboard. The orientation conditions of these types of manufactured fiberboard were analyzed using the Fourier transform image analyzing method and the results evaluated. Fundermental board properties such as bending and internal bond strength, and thickness swelling are discussed in relation to fiber orientation. The conclusions are as follows: 1) The expected orientations of fibers were observed, on the whole, in the low-density fiberboard types that were manufactured. 2) When the fibers in the board plane were aligned parallel to the span of the test piece, the board showed higher moduli of rupture and elasticity. The fiber orientation in the cross sectional plane of the span direction of the test piece improved moduli of rupture and elasticity as well. 3) The boards with more vertical (thickness direction) orientation showed higher internal bond strength and less thickness swelling. In such a manner, these oriented fiberboard types showed characteristic properties according to the fiber orientation. The optimum orientation conditions of pressing direction for mat forming can then be chosen to obtain the required board properties.