The properties of particleboard made from alkaline-treated wheat straw and methylene diphenyl diisocyanate binder

Abstract

Properties were evaluated for particleboard made from polymethylene polyphenyl polyisocyanate (pMDI) binder and wheat straw treated with sodium hydroxide (NaOH) and ammonia hydroxide (NH3·H2O) solutions. The crystallinity (Xc) of wheat straw and board properties including internal bond strength (IB), thickness swelling after 24 h (24 hTS), modulus of rupture (MOR), and modulus of elasticity (MOE) were investigated. XRD indicated that the crystallinity of wheat straw was increased with the mass fraction range from 1% to 3%, and the bending properties of board were also improved. MOR and MOE were significantly (P < 0.05) improved, and a positive correlation with solution mass fraction was shown. Bending properties, especially MOE, were superior to the requirements in GB/T 4897-2015. IB of NaOH solution treated board was also significantly higher (P < 0.05), but results for IB of ammonia solution treated and 24 hTS for board treated with both solutions failed to meet the standard. Effects of the two solutions were not the same according to a t-test, and the effects of NaOH were better.