Filament-based material extrusion additive manufacturing (MEAM) is an established technique in additive manufacturing (AM). However, semicrystalline polymers, such as polypropylene (PP), have limited commercial use in MEAM processes in the past due to their rapid crystallization kinetics and the subsequent effect on the integrity of the generated structures. The rapid crystallization of PP can be controlled by formulating blends of PP with hydrocarbon resins to enable longer re-entanglement times for interlayer adhesion. While the topic of formulating PP blends/composites with other materials to improve the printability has been investigated, variation in properties of commercial PP grades, of similar molecular weight (MW) and molecular weight distribution (MWD), on printability is still to be investigated. Those commercial PP grades can have wide variation in properties such as Melt Flow Index (MFI), additive content, and polymer architecture which can impact material properties relevant to printability. To investigate the effect of properties of commercial PP on their printability and mechanical performance, different commercial PP grades, with different properties, are blended with a fixed loading of hydrogenated resins, and the consequent effects on the mechanical properties of MEAM generated PP structures are studied via mechanical analysis. Tensile strength and the extent of interlayer adhesion in the 3D printed blends are characterized through rheological measurements. These measurements emphasize the importance of the relative location of the storage/loss modulus crossover point via small oscillatory frequency sweeps. We specifically show that a relatively higher crossover frequency will correlate with improved interlayer adhesion and reduced warpage in printed structures. However, this improvement is accompanied by a tradeoff, resulting in inferior tensile strength and an increased degree of print orientation anisotropy. / Master of Science / Additive Manufacturing (AM), commonly known as 3D printing, is a transformative technology with high potential to revolutionize the manufacturing landscape. Polymers are widely used in AM for various applications. As a result, extensive research is conducted to enhance the printability and properties of printed polymer structures. Polypropylene (PP) exhibits desirable mechanical, optical, and chemical properties that make its use in AM attractive. Despite this potential, optimizing the use of PP in 3D printing remains challenging. Consequently, extensive research is underway to improve the printability of PP. However, the effects of including additives to enhance the properties of commercial PP grades are often overlooked. We demonstrate that the choice of commercial PP grade is crucial to the mechanical and structural properties of structures generated via AM. This was established by developing a systematic experimental procedure to assess the printability of various PP grades and to measure their key mechanical and structural properties.