Properties of bio-based medium density fiberboard
In order to utilize agricultural waste fibers as an alternative resource for composites, a number of variables were investigated to determine whether the mechanical and physical properties of agro-based fiberboard could be improved. Fibers were classified into four different mesh sizes and used to evaluated the effect of fiber size on the mechanical and physical properties of the composite. Moisture content (MC) of the furnish and additional moisture from the resin applications were significant factors influencing the mechanical properties of the composites. Medium density fiberboard (MDF) made from bagasse fibers with 8 percent MC had a 63-percent increase in modulus of rupture (MOR) and a 30-percent increase in modulus of elasticity (MOE) compared to composites manufactured with 0 percent MC furnish. For bagasse MDF, a compounded resin system of 1 percent urea-formaldehyde (UF) performed as well as panels with 4.5 percent MDI in MOR and 3.5 percent MDI in MOE. Internal bond (IB) test results also showed that the modified resin system had slightly lower IB strength than with 4.5 percent MDI. Static bending and tensile strength parallel- and perpendicular-to-the surface increased as fiber aspect ratios increased from 3 to 20. Fiber bundles (11% of weight fraction, > 40 mesh) and particles smaller than 80 mesh size were responsible for the mechanical property loss of agro-based composites. Hardboard appeared to be the most promising panel type based on compatibility and property enhancement. Two mixing combinations (50/50 and 25/75) of bagasse/tallow tree fibers yielded mechanical and physical properties which statistically differed insignificantly from higher proportions of Sapium fibers and provided maximum utilization of bagasse fibers into the panels.