According to the used polymerization or mixing process and formulation, polypropylenes can be hard or soft, opaque or transparent, light or heavy, insulating or conductive, neat or reinforced with cheap mineral fillers, short or long glass fibres, natural fibres or even self reinforced; Polypropylenes can be also more or less elastic leading to TPOs and TPVs (thermoplastic vulcanizates), wood like (WPC), foamed or expanded. Last but not least, basic polypropylene resins are among the cheapest plastics and can be easily recycled.
Polypropylene is often perceived as a low cost and light weight solution but there is also a significant trend toward using this high-volume polymer in increasingly demanding applications where increasing performances are required.
Self reinforced polypropylene composites benefit from several general advantages: Suitability for the monomaterial concept, low density, good or excellent mechanical properties with high impact resistance, weight savings thanks to the combination of low densities and good mechanical properties (up to 50% potential weight savings over equivalent glass reinforced parts), easy recycling coming from the monomaterial concept.
Thanks to multiple ways of progress, Polypropylene resins compete with polyamide and other engineering plastics, steel, transparent polymers, etc.
Natural fibre reinforced polypropylene are a first step toward cheap sustainable composites: Low densities lead to noticeable cost and weight savings up to 27% over glass fibre or talc reinforced polypropylene.
Beside the particular applications reviewed in this short paper, it must be noticed that numerous other uses are more or less known such as, for example, special reinforced composites (commingled glass fibre reinforced polypropylene such as Twintex…), halogen free fire retardant formulations (HFFR), Expanded Polypropylene (EPP) foam, nanocomposites including clay nanocomposites and carbon nanotubes, wood plastic composites (WPC), injected or extruded microcellular parts, binders for powder injection moulding (PIM), thermal and electrical conductive versions, etc.
Lastly, let us remark that greener polypropylenes based on sustainable raw materials are being developed by Braskem and Novozymes among others.