We investigated the molecular characteristics of virgin polypropylene and recycled polypropylene that was obtained from byproducts (for example, runners, etc.) at the injection-molding of virgin polypropylene. We also tested the tensile properties of 3 mm-thick specimens made from each sample. The results showed that the two materials had almost the same molecular characteristics and tensile properties. However, their fractured surfaces were very different. Furthermore, a 100 µm-thick film of the recycled sample was very brittle compared to a film made from the virgin polypropylene. The recycled sample had a history of shear deformation at the time of injection-molding, and may have a unique inner structure due to shear deformation. We found a unique peak in an endothermic curve with a rapid heating rate, and this result supports the above assumption. We also found that the dependence of the tensile fracture energy on the duration of UV irradiation was essentially the same in these samples. Based on these results, we propose a new theoretical equation that can estimate the fracture ratio of molecules.