The mechanical properties of soybean straw and wheat straw blended medium density fiberboards made with methylene diphenyl diisocyanate binder

• Wheat straw fiberboard has better fastener retention than soybean straw fiberboard.
• Press load during manufacture has the greatest effect on board mechanical properties.
• Blended wheat/soybean straw fiberboard is comparable to single fiber boards.
• Soybean straw fiberboard is a viable alternative to wheat straw fiberboard.

A study was conducted to test the mechanical properties of medium density fiberboard (MDF) produced using soybean straw [Glycine max], wheat straw [Triticum aestivum], and a blend of the two fibers and the variations in properties that this blend produced. Additionally, the difference of soybean straw fibers compared to wheat straw fibers in the performance of MDF properties was investigated. Three formulations of the fibers were produced and tested to investigate the variation between properties of boards produced from the different fibers. The boards produced for testing were pressed using a hot press with 4 wt% methylene diphenyl diisocyanate (MDI) resin used to bond the particles and 2 wt% AW-50 wax emulsion used as a water retardant. The boards produced had a nominal density ranging from 579 kg/m3 to 646 kg/m3. Several test methods from ASTM standard D1037-12 were utilized to test the physical and mechanical properties of the boards. Initial results from the testing showed that several combinations of fibers could be used to produce boards with mostly no statistically significant difference between any one formulation, the only difference being a significantly higher difference in the screw withdrawal load needed for 100% wheat fiberboards compared to other formulations. The testing showed the viability of soybean stover fibers as a viable substitute or blend with wheat straw fibers with no appreciable decrease in the board properties except in the case of direct screw withdrawal resistance.