Problem definition and objectives: The processes of producing wooden products are not so diversative like the ones used for metals and plastics and usually have large amount of waste. Molding is one of the most commonly used methods by manufacturers of metal and plastic products. Molding is one of the methods that reduce waste and costs and at the same time increases the efficiency and production speed. In this context, the use of molding for wooden products seems somewhat unlikely due to the physical properties of wood. Wood does not melt from heat, and it cannot easily be shaped within a mold. The aim of this study is to investigate the mass production of wooden components using the compression molding method with poplar wood species.
Methodology: This research was conducted in four main stages: initial chemical treatment, thermal steam treatment, mold shaping, and final thermal treatment to stabilize the shape. The chemical treatment with hydrogen peroxide was used to relatively remove lignin and initially soften the wood texture. To this end, the samples were saturated with hydrogen peroxide under vacuum and pressure at different time intervals. The amount of lignin removal was assessed using microscopic studies and infrared spectroscopy. In the next stage, to enhance flexibility and facilitate easier molding, the saturated samples were subjected to hygrothermal treatment at 180°C for three hours. A controlled temperature hot mold was utilized to create the final product in the shape of a small container. During molding, the temperature was set at 180°C. In the final stage, after shaping, the formed wooden product was kept in the mold at same temperature for an additional two hours to ensure drying and stabilization of its dimensions. Finally, some physical properties of the formed product were studied.
Results: The obtained results confirmed that there is a possibility of producing formed wood pieces using this method. Microscopic studies also showed that treatment with hydrogen peroxide leads to the relative removal of lignin from the wood. These results were also supported by data from infrared spectroscopy and thermogravimetric analysis. The dry density of the control poplar wood was ±0.41 g/cm³, which increased to ±0.57 g/cm³ due to processing. Water absorption in the shaped samples was very rapid during the first two hours of immersion in water, but it then decreased and showed little change over the following 144 hours. The maximum water absorption of these samples after six days of immersion in water was 32% less than that of the control sample. The pattern of dimensional changes of the samples obtained from molded pieces was also different from that of the control poplar wood in various directions. The maximum transverse shrinkage of the molded samples was 19.3% less than that of the control poplar wood. On the other hand, the differences in shrinkage in width and thickness of the molded samples were much less than those of the control sample.
Conclusion: Although the results of this research were promising for the mass production of wooden subjects using the compression molding method, there are cracks on the final product that require further studies for resolution. The chemical treatment of wood with hydrogen peroxide and steam heating treatment provides the capability for softening the wood texture and shaping it within the mold. According to the results of this study, waste wood from sawmills and furniture factories, which cannot be used due to its small size, can be utilized for the mass production of wooden products without the need for shredding.