Editing Polypropylene (section)

===Mechanical properties===
The density of PP is between 0.895 and 0.93&nbsp;g/cm<sup>3</sup>. Therefore, PP is the [[Commodity plastics|commodity plastic]] with the lowest density. With lower density, [[Injection moulding|moldings parts]] with lower weight and more parts of a certain mass of plastic can be produced. Unlike polyethylene, crystalline and amorphous regions differ only slightly in their density. However, the density of polyethylene can significantly change with fillers.<ref name="guide" />{{rp|24}}

The [[Young's modulus]] of PP is between 1300 and 1800&nbsp;N/mm².

Polypropylene is normally tough and flexible, especially when [[copolymer]]ized with [[ethylene]]. This allows polypropylene to be used as an [[engineering plastic]], competing with materials such as [[acrylonitrile butadiene styrene]] (ABS). Polypropylene is reasonably economical.{{Citation needed|date=June 2018}}

Polypropylene has good resistance to [[fatigue (material)|fatigue]].<ref name="Maier" />{{rp|3070}}