| Abstract |
This study investigated Australian hemp hurd (Cannabis sativa L., "Frog One") as a lignocellulosic raw material for ultra-low-density hemp particleboard (ULHPB) with densities ranging from 213 to 309 kg/m(3). The hurd was first milled and fractionated into three particle size categories, that is, fine (F), medium (M), and coarse (C). Twelve unique ULHPB variants were then fabricated comprising varying particle loadings from four particle size mixes, that is, 100% C, 100% M, 50%/50% CM, 25%/50%/25% CMF, and adhesive contents of bio-epoxy (EPX), phenol resorcinol formaldehyde (PRF), and emulsifiable methylene diphenyl diisocyanate (MDI), respectively. The panel assessments, conducted in accordance with the Australian reconstituted wood-based panels standard AS/NZS 1859.1 (2017), revealed a significant effect of particle dimension on most physico-mechanical properties. Furthermore, the resination method and pressing temperature controlled post-cure panel expansion and additional panel characteristics. Notably, MDI-ULHPB exhibited drastically different behavior and properties compared to EPX and PRF equivalents, demonstrating greater bending strength, stiffness, screw withdrawal strength, and dimensional stability. Importantly, all MDI variants conformed to the 15% thickness swelling limit for moisture resistant particleboard. Surface lamination of MDI-bonded ULHPB with sheets of aluminum, Masonite, and Kraft liner significantly improved the inherently low flexural properties, suggesting the potential suitability of ULHPB as a core layer in lightweight sandwich composite panels. The integration of agricultural by-products, such as hemp hurd, into engineered building materials presents a promising opportunity to mitigate the depletion of finite timber resources and aligns well with circular economy principles. |