This study dealt primarily with the feasibility of using sunflower stalks as a raw material for particleboard. Three methods of breaking down sunflower stalks into particleboard furnishes were evaluated: hammer milling, disk refining, and ring flaking. Ring flaking was unsatisfactory because of an excessive loss of material as fines. Satisfactory furnishes could be produced by the other two methods, depending on the refiner plate design and plate clearance, size of the hammer mill screen, and the moisture content of the stalks.
Laboratory particleboards 18 inches by 18 inches by ½ inch thick were manufactured from four different furnishes: 100 percent sunflower stalks, 50 percent sunflower stalks - 50 percent aspen (wood) planer shavings, 100 percent aspen planer shavings, and 100 percent sunflower stalks with the pith removed. Boards were produced at two density levels (42 and 48 pounds per cubic foot) and two phenol formaldehyde resin content levels (5 percent and 10 percent solids based on the oven dry weight of furnish). There were two replications for a total of 32 boards.
The test results showed that modulus of rupture(strength in bending),internal bond strength, thickness dimensional stability, and durability(resistance to exterior exposure) decreased with an increase in sunflower stalk content; while, modulus of elasticity (resistance to deflection in bending) and linear dimensional stability increased with an increase in stalk content. Removing pith from the sunflower stalk furnishes significantly improved modulus of rupture and internal bond strength. Internal bond strength was greatly reduced by the addition of sunflower stalks and greatly improved by the removal of pith. All strength properties increased with an increase in density and resin content. When all properties were considered, it was concluded that sunflower stalks made' an acceptable particleboard for interior applications. The low internal bond strength, the most serious deficiency of stalks, was upgraded sufficiently by increasing resin content or density, removing pith, or by adding planer shavings.
Gertjejansen, Roland O..
Properties of Particleboard from Sunflower Stalks and Aspen Planer Shavings.
Minnesota Agricultural Experiment Station.
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