Khazaeian, A., Ashori, A., & Yahyavi Dizaj, M.

Carbohydrate Polymers 120: 15–21.

2015

The aim of this study was to investigate the suitability of sorghum (Sorghum bicolor) stalk (SS) as a promis-ing raw material for particleboard manufacturing. The SS particles and industrial hardwood particles invarious proportions were used as the raw materials for the surface and core layers of the three-layerparticleboards. Commercial urea formaldehyde (UF) adhesive was used as a binder. Morphological andchemical characteristics of the SS were evaluated. Effects of five variable parameters on the physical(thickness swelling (TS), water absorption (WA)), and mechanical (modulus of rupture (MOR), modulusof elasticity (MOE), internal bond (IB)) properties of the particleboards were determined. Other param-eters such as type of resin (UF), hardener content (1%), type of hardener (NH4Cl), press closing time(5 mm/s), board density (0.70 g/cm3), and press pressure (30 kg/m2) were held constant. Fractional fac-torial was used to find the optimum condition for the studied variable parameters. The morphologicalresults showed that SS had comparable fiber length with softwoods and fiber width and wall thicknessvalues greater than the hardwood of common forest species. They had higher hot-water solubility values,lignin and ash contents than those of the other woody materials. The experimental results showed thatincreasing of SS particles usage in the surface layer significantly affects the board properties. Containing50 wt% SS particles in the surface, the MOE and MOR values exceed the minimum requirements of theEuropean norms (EN) standards, for general purposes. All of the particleboards produced from SS hadIB higher than the EN standard requirement. The presence of SS in the particleboards resulted in higherWA and TS values. All the mechanical properties of the boards decreased when the press temperaturewas increased from 160 to 180◦C. Finally, it can be stated that SS has enough potential as a supplementfibrous material, in combination with industrial hardwood particles, for particleboard manufacturing andindoor applications.