Effects of Moulding Temperature on the Physical Properties of Wood-Based Moulding Bonded with Citric Acid

Abstract Development of natural adhesives that do not depend on fossil resources is very important for the future of wood-based materials. We recently found that citric acid can be used as a natural adhesive for wood-based moulding. In this study, we investigated the effects of moulding temperature on the characterization of wood-based moulding bonded with citric acid. Wood powder obtained from Acacia mangium was mixed with 20 percent (by weight) citric acid, and the powder mixture was moulded at a temperature ranging from 140°C to 220°C. The press pressure and heating time were set at 4 MPa and 10 minutes, respectively. The bending properties were affected by the moulding temperature, and the moulding fabricated at 180°C showed excellent values. The average impact strength of the moulding at 180°C was 1.1 kJ/m2. Water resistance increased with moulding temperature, and good resistance against boiling water was achieved. Thermal properties were also clearly increased with moulding temperature. However, few significant differences were found in the mouldings after a repeated boiling treatment. Based on the results of Fourier transform infrared spectroscopy, ester linkages between wood and citric acid were confirmed, especially at high moulding temperatures.