We have investigated insulation panels from 1”, ¾”, and 3/8” hemp hurd particles and soy-based adhesive using a vertical wall frame. A mixture of hemp hurd and soy-based adhesive was prepared in a KitchenAid mixer and then applied to the vertical wall frame. The mixture was able to stick to the wall at various usages of the adhesives to form a uniform insulation panel. The panel on the wall was dried at the ambient indoor environment in Corvallis, Oregon. All panels regardless their hemp hurd particle size and adhesive usage can all reach a stable moisture content after they were stored in ambient indoor environment from April to August in Corvallis, Oregon for at least six days. Six days are relatively short for building a residential house and thus may not be a negative factor for builders to accept these panels as insulation materials. The R-values (a measure of thermal resistance) of air-dried panels are affected by the adhesive usage, but not the sizes of hemp hurd particles or the small variation of panel density under the optimum adhesive usage. The R-values of all air-dried panels under optimum process conditions are inferior to those of expanded polystyrene (EPS) and extruded polystyrene (XPS) foam boards that are commonly used in residential and commercial building. All SF-hemp hurd panels are based on environmentally friendly, renewable materials. They have decent insulation properties although their R-values are still lower than the required values for building insulation materials. They may be used as insulation materials in shipping and other applications. This study reveals that the soy flour-based adhesive plays an essential role in the R-values of hemp hurd panels. Further study such as changing the formulation of the soy-based adhesives or investigating new soy-based adhesives may be able to increase the R-values of hemp hurd panels to the level that can meet the requirements for building insulation materials.

Commonly used building insulation materials include fiberglass batts, foam boards from polystyrene or polyurethane, and sprayed polyurethane foam. They have many issues such as requiring the high energy input in their production, causing environmental pollution, posing hazards to human health, or being based on non-renewable petrochemicals. In this study, we demonstrated that soy flour-based adhesive was an essential component for conversion of renewable hemp hurd, an underutilized part of hemp stalks, into environmentally friendly insulation materials. Use of soy flour-based adhesive for production of insulation materials represents a new market for soy flour. This study may create a new field of application for soy flour although the R-values (a measure of thermal resistance) of all soy flour-hemp hurd panels from this study are still lower than the required values for building insulation materials. Further study the soy-based adhesives may be able to increase the R-values of soy flour-hemp hurd panels to the level that can meet the requirements for building insulation materials, thus greatly expanding the industrial use of soy flour.