Manufacture of High-Performance Rice-Straw Fiberboards

Rice straw, a waste agriculture material grown and harvested in Willows, CA, was used,is a raw material in the production of thin medium- and high-density fiberboards (MDFs and HDFs). The rice straw was cleaned, size-reduced, and soaked in water before being refined. Defibration was performed in it pressurized pilot-plant single-disk refiner, OHP 20. The fiber production capacity reached a level of 63 kg/h. and the proper fiber quality for MDF/HDF production was established. Analysis of the produced fiber showed an average fiber length of approximately 0.9 mm, in average fiber width of 31 mu m, a shive weight of below 24%, and a dust content of less than 30%. Production of fiberboards was performed by addition of 3%, 4%, and 5% methylene diphenyl diisocyanate (MDI). The flexural properties, internal bond strength, and thickness swelling of the produced fiberboards were evaluated according to ASTM methods. The finished fiberboards based on rice straw and MDI resin showed excellent properties. The internal bond (IB) reached levels of 2.6 MPa, and the modulus of rupture (MOR) and modulus of elasticity (MOE) showed levels comparable to those of wood-based fiberboards and were acceptable according to the requirements or medium-density fiberboard (MDF) for interior applications (American National Standards Institute, ANSI A208.2-2002). The water-repelling properties of the 3-min rice-straw fiberboards were encouraging; the thickness swelling, (TS) was in the range of 15-30%. Two different methods to avoid adhesion between the press plates and the resinated fiber material during hot pressing were investigated: protective paper sheets were placed between the fiber mat and press plates, or a press-release agent was sprayed oil steel plates that were then placed ill the press before pressing Satisfactory results were obtained with both methods, and no adhesion was observed between the fiberboard and the steel plates. The method of using press-release agent during pressing had no notable negative effects oil the fiberboard properties.