Evaluation of the properties of hybrid composites based on recycled polypropylene containing pine wood flour and different additives

In recent years, there has been a rapid increase in efforts to recycle and reuse waste materials. Both ecological and economic benefits have led to the increased utilization of recycled materials. One of the widely used polymers in the plastics industry is polypropylene. However, the use of recycled polymers is limited in sectors such as automotive, textiles, and packaging due to the reduction in their technical properties. Therefore, it is necessary to improve the properties of recycled materials and to develop new materials by adding natural additives to plastic materials to reduce the amount of plastic used.The aim of this study is to investigate the properties of hybrid composites obtained by adding different amounts of calcium carbonate to recycled polypropylene containing pine wood flour and talc, produced using the plastic extrusion method. The goal of the study is to develop more environmentally friendly composites by reducing the amount of plastic used with polypropylene and natural pine wood flour and to introduce hybrid composites with characteristics suitable for automotive applications through the addition of calcium carbonate. The production of the composites was carried out in two stages: extrusion and injection molding. First, recycled polypropylene containing talc and micronized pine wood flour was homogeneously mixed using a twin-screw extruder and then granulated to produce the composite. In the second stage, calcium carbonate concentrate (5-20 % wt.) was added to the extruded composite and shaped using the injection molding method. The produced hybrid composites were then subjected to various tests to analyze their properties, including tensile, flexural, impact test, Heat Deflection Temperature (HDT), Vicat softening temperature, density, melt flow index, and differential scanning calorimetry (DSC). As a result of these studies, it was determined that pine wood dust increases viscosity and density. The addition of pine wood dust and calcium carbonate was found to enhance the tensile strength, breaking stress, flexural modulus, and flexural strength of the composites, while reducing the elongation at break and impact resistance. It was also observed that the thermal resistance of the composites improved with the addition of wood flour, while their melting temperatures remained unchanged.