The density of PP is between 0.895 and 0.93g/cm3. Therefore, PP is the commodity plastic with the lowest density. With a lower density, lighter weight molded parts and more parts of a given quality of plastic can be produced. Unlike polyethylene, the densities of crystalline and amorphous regions differ only slightly. However, the density of polyethylene can vary significantly with fillers. [9]: 24

The Young's modulus of PP is between 1300 and 1800 N/mm².

Polypropylene is generally tough and flexible, especially when copolymerized with ethylene. This allows polypropylene to be used as an engineering plastic, competing with materials such as acrylonitrile butadiene styrene (ABS). Polypropylene is quite economical. [citation needed]

Polypropylene has good fatigue resistance.

Polypropylene is resistant to fats and almost all organic solvents at room temperature, except strong oxidizing agents. Non-oxidizing acids and bases can be stored in containers made of PP. At high temperatures, PP can be dissolved in non-polar solvents such as xylene, tetralin and decalin. Due to the tertiary carbon atoms, PP has lower chemical resistance than PE (see Markovnikov's rule). [13]

Most commercial polypropylenes are isotactic, with crystallinity between low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Isotactic and atactic polypropylene are soluble in p-xylene at 140 °C. When the solution was cooled to 25 °C, an isotactic precipitate precipitated out, while the atactic part remained soluble in p-xylene.