Generally, moulds for injection moulding are made for mass production of quite simple parts and components that can be later assembled to produce complex products.

A thermoplastic polymer, polypropylene (also called polypropene) has properties between that of LDPE and HDPE and is one of the most versatile polymers available.

The reason why the parts must be quite simple is that they must be extracted from the mould in which it is made by solidification of the plasticized flow injected in.