Properties of moulding products from sorghum bagasse combined with alang-alang leaves, sengon wood or bamboo using citric acid-sucrose

Moulding products are commonly made from wood and synthetic adhesives. Wood is becoming scarce and expensive especially from the natural forests, while synthetic adhesives used in the wood industry are mainly made from petroleum-based that are not renewable and toxic. Therefore, utilization of substitute raw materials and natural adhesives was essential. In this work, moulding properties made from sorghum (Sorghum bicolor) bagasse combined with alang­ alang (Imperata cylindrica) leaves, sengon (Paraserianthes falcataria) wood or bamboo (Dendrocalamus asper) using a natural adhesive citric acid-sucrose were investigated. The objective of this work was to observe effect of different ratio of materials on the properties of moulding products. Ratios of sorghum bagasse to alang-alang leaves or sengon wood or bamboo were 100:0, 75:25, 50:50, 25:75 and 0:100. Citric acid-sucrose with ratio of 50:50 by weight as adhesive was used at 20 weight percent of the total moulding weight. Raw materials and adhesives in powder form were mixed manually. The dumbbell-shaped moulding was prepared using a hot press machine at temperatures of 180, 200°C, with a pressure of 4 MPa for 10 minutes. The target board density was set at 1 g/cm3. Bending strength and dimensional changes due to cyclic test were determined. Results showed that increasing ratio of alang-alang leaves or sengon wood or bamboo decreased the bending properties and increased the dimensional changes. A pressing temperature of 200°C produces better moulding properties compared to 180°C. Ester linkage indicates that adhesive reacted with raw materials, resulting in good bonding mechanism. Mouldings with 100% Keller variety sorghum had the best properties. At the ratio of sorghum bagasse and other raw materials of 75:25, the moulding properties closed to sorghum bagasse only. Therefore, it is suggested to use a maximum of 25% of other materials when combined with sorghum bagasse.