Biocomposite hardboard from renewable biomass bonded with soybean-based adhesive

The goal of this study was two fold. The first was to determine the comparative properties of dry formed hardboard made from renewable biomass (wheat and soybean straws) and from conventional soft wood fiber. The second was to compare the adhesion properties of a soybean-based adhesive with a conventional urea formaldehyde resin. The hardboard properties evaluated were thickness swell, modulus of rupture, modulus of elasticity, and internal bond strength. The soybean-based adhesive resulted in significantly better mechanical properties and better water resistance than the urea formaldehyde resin. Wheat straw and soybean straw were comparable in their mechanical and water resistance properties for hardboard production. However, hardboard made from wheat straw fiber and soy straw fiber had comparable mechanical properties but inferior water resistance to hardboard made from wood fiber. Wheat straw fiber and soy straw fiber can be used as co-fibers without treatment to be competitive with pure wood fiber for both mechanical and water resistance properties. A 50%/50% agrifiber/wood fiber composition provided comparable mechanical and water resistance properties to pure wood fiber for hardboard production. The thickness swell of hardboard increased with increasing agrifiber composition. Fiber, rather than adhesive, was the major contributor to thickness swell. Wheat straw fiber and soy straw fiber should be physically or chemically treated to increase their water resistance.