Properties of binderless board made from rice straw: The morphological effect of particles

• Binderless board from rice straw could be manufactured from powder under 1 mm.
• Water resistance was high because of wax-like substances on rice straw.
• IB was high in order of stem, leaf blade and leaf sheath.
• IB increased with decreasing ash and silica content.
• Trichomes and wart-like protuberances might inhibit self-bonding between particles.

Binderless boards were manufactured from rice straw by hot-pressing in order to evaluate the morphological effect of particles from rice straw. For the morphological effect, we examined the influence of particle size and morphological parts of rice straw, respectively. Internal bonding (IB), thickness swelling (TS) and water absorption (WA) were measured as the properties of the boards. As a result, binderless boards were successfully manufactured from rice straw powder smaller than 1 mm. Regarding the effect of morphological part from rice straw, IB of the board made from stem powder was the highest, subsequently followed by leaf blade powder, and leaf sheath powder. IB tended to increase with decreasing ash and silica contents. Trichomes and wart-like protuberances on the epidermis of rice straw might inhibit the bonding between particles. The water resistance of binderless boards made from rice straw was high regardless of low IB. It is possible that wax-like substances on the epidermis of rice straw might contribute to the water resistance of the board.