Fiberboards from Loblolly Pine Refiner Groundwood: Aspects of Fiber Morphology

In tests with loblolly pine, most properties of wet-formed hardboard were improved by using fiber refined from wood having short, slender tracheids with thin walls. A theoretical analysis suggested that the fibers fail in bending while under stress induced by the pressing operation. Such bending failures improve conditions for hydrogen bonding, thus improving board properties. Tracheids having narrow diameters and thin walls flex easily and collapse readily. Short tracheids are more desirable than long tracheids because of a greater number of fiber crossings per unit weight in the pulp mat. Tracheid length was determined from 40 chips randomly selected. Chips were dissected into earlywood and latewood slivers and macerated in a solution of hydrogen peroxide and glacial acetic acid for 2 days at 50?C. Samples of the macerated material were mounted in water on glass slides and measured with a projection microscope. Boards were manufactured in three density classes of 0.45, 0.60, and 0.80. Only boards of the 0.60 density were used in this study.

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