Making wheat straw particleboards by using mixture of MF and UF resins

Abstract

For making wheat straw particleboards, different mixtures of UF and MF resins were used. The ratio of UF : MF was 0:100,75:25,50:50,25:75 and 100:0 based on weight of resin and boards densities were set to 0.7 . The physical and mechanical properties such as Thickness Swelling(TS)(after 2 and 24 hours), Internal Bonding(IB) , Modulus Of Elasticity(MOE) ,Modulus Of Rupture(MOR) were determined and compared to EN 312-4 standard. The highest amounts of IB ,MOR and MOE are from the boards that were made from 50:50 (UF:MF) . All of The boards MOE and MOR amounts of all treatments except treatment 100:0 (UF:MF) were in range of EN 312-4 standard but the IB amounts were not. The TS amount was improved in the boards with more MF content but it was not in EN 312-4 range. Due to the thin waxy layer that covers the outer most layer of wheat straw surface, the non polar structure of this layer brings incompatibility between polar resins and wheat straw particles and this incompatibility will result in low physical and mechanical property for wheat straw particleboards. Also due to low porosity of waxy layer, the distribution of formaldehyde polar resins on straw particles surface, not well occur and this itself is an important factor in decrease of physical and mechanical resistance in wheat straw particleboards.

Keywords

• wheat straw particleboard
• Urea formaldehyde resin
• Melamine formaldehyde resin
• waxy layer