Obtaining and Investigating the Physical and Mechanical Properties of Binder‑Free Plastics Produced by the “Blow‑Off” Method

An analysis of literature shows that domestic and international scientists are focusing on the removal of excess steam during the production of wood-based materials and their derivatives by hot compression molding. Under piezothermic conditions (application of high pressure and temperature to wet molding raw materials), the necessary chemical reactions, resulting in the formation of new lignin-carbohydrate compounds, are facilitated during the production of binder-free plastic (BFP) in a closed mold. Under these conditions, the high-pressure steam is generated, which impedes the molding material compaction and generates internal stresses caused by elastic deformations and compressed vapors and gases remaining in the material. Consequently, this leads to a decrease in the physical and mechanical properties of resulting material. This study examines the feasibility of using the “blow‑off” method to produce binder-free plastic by closed-mold pressing. A mathematical design of the experiment was used to conduct this study. As a result of the adopted experimental model, the BFP samples were obtained and the influence of filler moisture content and pressing conditions on their physical and mechanical properties was determined. Based on the resulting regression equation describing the process, the optimal BFP pressing conditions were determined using the “blow‑off” method. Samples based on pine and birch sawdust and sunflower husks were obtained and tested using the optimal factors. Results of study demonstrated a positive effect of the “blow‑off” method when pressing various plant materials on the physical and mechanical properties of binder-free plastics.