Abstract
Abstract Oriented Structural Straw Board (OSSB) panels are composites made from straw originally from agricultural residues and non-formaldehyde based adhesive, whose main application is for construction as a closing and ceiling material. The objective of this study was to evaluate the effect of the polyurethane adhesive content on physical and mechanical properties of OSSB produced with locally available SbS (soybean straw). Four castor oil based polyurethane ratios (6%, 9%, 12% and 15%, by mass of the SbS) were tested. OSSB was evaluated according to European standards for wood-based composites; also, a physical and chemical characterization of the SbS was performed. SbS has an irregular shape, which reduced the OSSB mechanical performance due to the low densification of the composite and the development of transversal cracks on the SbS after the OSSB manufacturing process. The static bending and thickness swelling performance of SbS OSSB was not improved by the increase of polyurethane adhesive content. SbS low ash content and neutral pH extractives indicates that probably its chemical properties should not affect the setting of the adhesive.
Highlights
According to the USDA (UNITED..., 2019), more than 360 million metric tons of soybean oilseeds were harvested worldwide in 2018/2019, and Brazil is the second main soybean producer in the world, after the United States
Oriented Structural Straw Board (OSSB) density reached 631 kg.m-3 in composites produced with 15% resin content, close to the results reported by Cheng, Han and Fang (2013) and Sitz and Bajwa (2015) for OSSB and MDF (Medium Density Fiberboard) produced with wheat straw and pMDI resin, respectively
SbS has heterogeneous dimensions according to its measured parameters, which were: internode length, external diameter and wall thickness. 6% and 9% castor oil based polyurethane adhesive content OSSB had lower density than the SbS itself due to the raw material geometry
Summary
According to the USDA (UNITED..., 2019), more than 360 million metric tons of soybean oilseeds were harvested worldwide in 2018/2019, and Brazil is the second main soybean producer in the world, after the United States. Agricultural residues are often considered a problem for farmers due to their low monetary return, but they can be viewed as an economic opportunity, especially for developing countries where they can have a positive impact (ADEL et al, 2016). Some residues (e.g. wheat straw, rice straw and rice husk) receive interest due to their low cost, great availability, reduction of environmental pollution and large number of natural polymers in their composition (ARGENTO et al, 2019; LIMA et al, 2019). Barbu, Reh and Çavdar (2017) indicate that the production of composites with agricultural residues is considered attractive, especially due to the increase in the price of wood as a raw material. According to Väisänen et al (2016) it is required that these products do not present inferior performance in comparison to currently available wood-based composites, otherwise the selection of the agricultural residue as a raw material will not happen
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