Background and objectives: Given the increasing use of nanocomposites in various industries, improving the mechanical and physical properties of these materials has become particularly important. Nanocomposites, due to their combination of different materials, exhibit unique features such as lightness, strength, and resistance to environmental factors. In this context, calcium carbonate nanoparticles are recognized as an effective reinforcing agent that can enhance the performance of poplar wood flour and recycled polypropylene nanocomposites. This research examines the impact of calcium carbonate nanoparticle content on the mechanical properties of these nanocomposites. As a reinforcing material, calcium carbonate nanoparticles can improve mechanical properties by enhancing adhesion and stress transfer between different phases of the nanocomposite. The main objective of this study is to evaluate the effects of the size and amount of calcium carbonate nanoparticles on the elastic modulus, tensile strength, and other mechanical characteristics of the nanocomposites. Given the diversity of applications for nanocomposites in packaging, automotive, and construction industries, the results of this study could contribute to the development of lightweight and durable materials in these sectors. Additionally, this research could provide strategies for the optimal use of recycled materials, which in turn would help preserve the environment and reduce costs. Methodology: For this purpose, polypropylene was used at three levels (50%, 60%, and 70%), poplar wood flour at three levels (30%, 40%, and 50%), and calcium carbonate nanoparticles at four levels (0%, 1%, 2%, and 3% by weight). Additionally, maleic anhydride grafted polypropylene was included at a fixed level of 3%. These materials were mixed using a twin-screw extruder, and standard test samples were produced using the injection molding method. Subsequently, mechanical properties, including tensile and flexural strength, tensile and flexural modulus, impact resistance, and hardness, were measured according to ASTM standards D 638, D 747, D 256, D 224, and D 703. Results: The results related to the F-value and significance level indicated that the effect of wood flour content on mechanical properties, including tensile strength, flexural strength, tensile and flexural modulus, impact resistance, and hardness, was significant at the 95 percent confidence level. Additionally, the effect of nano calcium carbonate on tensile and flexural strength, flexural modulus, and hardness was also significant at the 95 percent confidence level, whereas the flexural modulus and impact resistance were not significant at this level. The interaction effects between wood flour and nano calcium carbonate on all resistances were not significant at the 95 percent confidence level. Conclusion: The findings of this research indicate that increasing the amount of poplar wood flour from 30 to 50 percent has a significant impact on the mechanical properties of nanocomposites, particularly in enhancing tensile and flexural strength, modulus, and hardness. This improvement is attributed to increased adhesion and stress transfer between phases. However, the increase in wood flour content leads to reduced impact resistance and greater brittleness of the composite. Adding nano calcium carbonate up to 3 weight percent also improves mechanical properties, but similarly to wood flour, it reduces impact resistance. Overall, the appropriate selection of the type and amount of additives can enhance the performance of nanocomposites, while attention to negative effects such as reduced impact resistance is also essential. |