Evaluation of Biopolyurethane/Barley Straw-Based Engineered Wood Composites

More than 95% of building materials in Europe are produced from fossil raw materials. Over the past two decades, numerous scientific studies have demonstrated that building materials made from agricultural plants or industrial processing waste can compete with traditional materials. In this work, engineered wood composites were prepared from biopolyurethane and barley straw, and their properties were evaluated. Barley straw from bales was milled through sieves of different sizes. Four straw fractions of 5, 10, 25 and 35 mm were prepared for testing. During the research, the granulometric composition, particle density and shape of various fractions were evaluated. Engineered wood composites were prepared using different filler fractions and a biopolyurethane binder. In this study, engineered wood samples were produced using biopolyurethane binders at straw-to-binder ratios of 0.5 to 1.5. Different pressure levels were used for sample preparation: 1.5, 2.25 and 3.0 MPa. This study evaluated the influence of the granulometric composition and particle shape of straw on the properties of engineered wood composites. Tests showed that the highest compressive strength, 17.0 MPa, was achieved with composites formed from a 5 mm straw fraction, which had the highest density. The samples with the highest density were also characterised by the lowest swelling (5-10%) and water absorption (1-2%). The flammability of the samples showed that at a 0.5 binder/straw ratio, the composite was non-combustible and did not support flame spread after the flame source was removed.