Preparation of Hot-Pressed Wheat Straw Board by Self-Adhesive Process: Effects of Raw Material Sizes and Acid/Alkali Pretreatment

The development of wheat straw boards utilizing intrinsic bonding mechanisms not only facilitates the high-value utilization of agricultural solid waste but also diminishes the reliance on synthetic adhesives. In this study, using wheat straw as the primary substrate, we investigated the effects of mechanical smashing combined with pretreatment using inorganic acids or alkalis on the properties of hot-pressed boards, as well as the relationship between the properties of hot-pressed boards and the physical properties and chemical composition of wheat straw raw materials. These selective pretreatments effectively degraded lignin, hemicellulose, and other components, thereby promoting fiber reorientation and resulting in a denser microstructure with improved self-bonding capabilities. The optimal board was fabricated with a granularity of 0.3 mm and underwent alkali pretreatment, achieving a tensile strength of 11.564 MPa, an internal bonding strength of 0.556 MPa, and bending strength and modulus of 24.306 MPa and 2.766 GPa, respectively. These findings have significant implications for advancing manufacturing processes and conceptualizing binder-free boards derived from agricultural residues.