Utilizing Miscanthus stalks as raw material for particleboards

Miscanthus x giganteus stalks were studied as a possible replacement for wood in particleboards. Produced particles from Miscanthus contained 38% of cellulose, and 17% of lignin, while spruce had 45% cellulose, and 28% lignin. The amount of hemicelluloses was the same for both, spruce and Miscanthus (21%). Miscanthus-made particleboards were produced at two levels of methylene diphenyl diioscyanate resination, i.e. 4% and 6%. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), thickness swelling and water absorption were measured. Mechanical properties of the Miscanthus-made particleboards were overall reduced: compared to spruce, MOR and MOE were down by 30%, while IB was lowered by 60%. Microscopic analysis of fracture surfaces of the Miscanthus-made particleboards after IB testing showed collapsed cells regions in the soft parenchyma, with no obvious adhesive failures. In contrast, spruce-made particleboards revealed much smoother fracture surfaces with structural failures running through cell walls and possibly also through gluelines. The collapsed parenchyma cell regions suggest a direct link to the reduced mechanical properties. Further, compared to spruce the Miscanthus-made particleboards have shown higher thickness swelling, but lower water absorption. For Miscanthus, no effects of higher MDI adhesive dosages on MOE, MOR and IB were observed. To further improve properties of Miscanthus-made particleboards, at sorting-out of parenchyma tissue components to the highest degree possible is recommended, prior to hot-pressing.