Polypropylene (PP) is one of the most largely used man-made polymeric materials. This synthetic stereo-regular polymer has a high tensile strength combined with a low cost, which could explain it’s wide usage and application. This book covers some important advances in PP research, including its synthesis, characterizations, modifications, and applications. A thorough understanding of propylene polymerization, mainly concerning its physical and chemical features, as crystalline morphology, for instance, is useful to understand how it could influence PP mechanical properties and heat resistance. These characteristics are directly related to PP rheology and consequently the tendencies to form composites or blends. PP hybrid materials amplify the possibilities of obtaining new useful supplies, and also allow recycling or reusing wastes or low cost resources, as ashes, besides increasing its value.