Investigation of the uses of polymer nanocomposite materials in electric vehicle battery packs

In this thesis, it was aimed to develop hybrid polymer nanocomposites for use in electric vehicle (EV) battery packs and to improve the thermal and mechanical properties of these nanocomposites while preserving their electrical insulation. Since the demand for electric vehicles is growing, addressing key issues such as limited driving range and battery performance becomes increasingly important. One of the primary challenges contributing to this issue is the weight of the vehicle, which directly increases energy consumption and battery life. Reducing vehicle weight is a promising solution, and lightweight, cost-effective, and recyclable polymer composites offer an alternative to traditional heavy metals used in automotive manufacturing. In this study, polypropylene (PP) was selected as the polymer matrix. In the first stage, to increase the thermal conductivity and mechanical strength of PP, equal amounts of hexagonal boron nitride (hBN) and silicon carbide (SiC) fillers were added to the PP matrix at different total weight ratios (20%, 40% and 50%) to produce PP/hBN/SiC nanocomposites. In the second stage, to improve the compatibility of the additives with the polymer matrix and to improve the final properties of the nanocomposite structure, PP/Ti/hBN/Ti/SiC polymer nanocomposite samples in which hBN and SiC particles were coated with tetraethyl orthotitanate (Ti) were produced at similar weight ratios (20%, 40% and 50%). The samples were prepared in accordance with the characterization methods by mechanical mixing and compression molding techniques. This study demonstrates that the addition of hexagonal boron nitride and silicon carbide nano fillers to the polypropylene matrix leads to significant improvements in the material's mechanical, thermal, electrical, and fire resistance properties. As the filler content increased, the elastic modulus of polypropylene improved by 57%, and mechanical stiffness was notably enhanced. However, some mechanical properties were observed to decrease at higher filler concentrations, such as 40% and 50%. Additionally, the use of titanate coupling agents was found to promote a more homogeneous distribution of the fillers, improving flexibility and impact resistance. Tensile strength showed a significant decrease, particularly at 40% and 50% filler concentrations, but the tensile strength of titanate-coated samples decreased less. Thermal analyses showed that the fillers improved the thermal properties of PP, while excessively high filler contents could lead to adverse effects. It is observed that, thermal conductivity increased by 216% for the 20% hBN/SiC-filled samples compared to pure PP, and this increase reached 248% for the titanate-coated samples. These results highlight the potential of polypropylene-based nanocomposites for industrial applications and emphasize the need for optimization. This study was completed within the scope of TUBITAK 1002-A project numbered 223M505, whose director is Assoc. Prof. Dr. Meral AKKOYUN KURTLU.