Fabrication of Lightweight And Durable Thermoplastic Composites For Injection Molding With The Integration Of Waste-Driven Reinforcing Materials

Official URL: https://risc01.sabanciuniv.edu/record=b3395401

Reducing carbon dioxide (CO2) emissions and adopting lightweighting strategies are crucial aspects of enhancing the sustainability and efficiency of the transportation sector. As sustainability becomes a central focus in the automotive industry, there is a growing demand to use recycled sources in manufacturing processes for part production. Especially for structural parts in automotive part production, polyamides (PAs) are extensively employed as engineering thermoplastics across diverse fields, owing to their ease of processing, good thermal stability, and cost-effectiveness. In PA based compound formulations, short glass fibers are preferred to reinforce PA matrix. However, the higher density of glass fibers and its brittleness during extrusion process can be problematic and high energy demands to produce both fiber and parts are main drawbacks in serial production. At this point, the present thesis aims to replace glass fibers with sustainable solutions by developing new PA compound formulations by using additives coming from recycled sources which are graphene nanoplatelets (GNP) derived from waste tires, spherical graphenes from waste coffee (CWC) and short carbon fiber (CF) bundles coming from plant waste. These additives were successfully incorporated into PA matrix by using thermokinetic high-shear mixer resulting in high degree of exfoliation and thus high mechanical performance that can compete with conventional compounds. In the case of GNP reinforced PA composites, their tensile and flexural properties improved by 42% and 43%, respectively, by adding optimized loading ratio of 0.3 wt.% GNP in PA6,6. With this amount of GNP, CF based compounds were successfully produced by increasing tensile and flexural properties by 95% and 86%, respectively, in comparison of unfilled PA. Through GNP integration, the absorbed impact energy of this compound improved by 7.7% due to enhanced interfacial interactions between the ternary interfaces. By embracing the evolving trends towards sustainability in major transportation industries, this study strategically navigates the transition from synthetic PA6,6 to semi-synthetic PA6,10 matrix and leveraging the remarkable potential of waste-derived reinforcing materials. Herein, the effects of aspect ratio of waste driven reinforcements, reinforcement size, and loading ratios were investigated to generate a comprehensive interface characterization. Consequently, this thesis demonstrates that using tailored selection of waste-derived reinforcing material, sustainable compounds can replace several synthetic products in the market in terms of both tensile properties, lightweighting, and environmental impact. In addition, CO2 emission values of both the selected recycled sources and the developed compound formulations were calculated by using life cycle assessment (LCA) analysis. A significant reduction was achieved by reducing 55% CO2 emission with new recycled additive reinforced PA6,10 formulations over PA6 having 15 wt.% GF available in the market. Therefore, this study extends beyond the material enhancement to encompass a holistic approach that contributes to a circular economy and promotes eco-friendly, high-performance composites for the automotive industry, thereby laying the foundation for incorporation of waste-derived reinforcements into compound formulations to create a future where waste materials are not merely managed but transformed into valuable resources.