Fabrication and characterization of soybean straw and polylactide acid-based hybrid bio-board

Biodegradable bio-board is held together by the self-bonding ability of natural fibre rather than by the synthetic resin adhesives used in traditional fibreboard. This provides a promising way to reduce the use and release of toxic substances. However, the hydrophilic characteristic of natural fibres gives bio-board poor water resistance compared to conventional fibreboards. Therefore, the objective of this study was to fabricate a hybrid bio-board in a wet forming process using soybean straw fibre with polylactic acid (PLA) added as a binder at different mass percentages. The effects of applied pressure during fabrication on the mechanical properties, water resistance properties, and wettability of hybrid bio-board were investigated. The thermal stability, spectroscopic characteristics, and morphological properties were also analysed. The addition of PLA weakened the bending strength and tensile strength of the hybrid bio-board made at each of three applied pressure levels. Fortunately, the hybrid bio-board with 10 and 30% PLA contents could maintain a considerable bending strength higher than 35 MPa when made with 8 MPa of applied pressure. The addition of PLA greatly improves the water-resistant performance of the board. Even with only 10% PLA, the water absorption and thickness swelling rates were reduced by more than half. We argue that PLA could be utilized as a latent natural binder to make hybrid bio-board using agricultural straw fibre; however, an environmentally friendly coupling agent is needed to improve the mechanical properties.