Metals, because of their densities and high melting points, consume a lot of energy for the fabrication and the use of parts and goods. Generally, the heavier the parts are, the more energy they consume during their service life. The ousting of metals by plastics leading to lighter products benefits the processing steps and performance during the complete service life.
Moreover the most common metals are ferro-alloys that are often susceptible to corrosion and rusting and thus, need to be re-painted often during their service life or even be replaced.
Consequently, metal substitution with weight reduction is the need of the hour for the industry.
Generally speaking, polymers do not perform like metals from a mechanical point of view but the design freedom allows a better suitability to adapt the local part geometry and the effective local constraints leading to a better exploitation of the characteristics. This was anticipated for markets such as Automotive and Transportation where the running energy and the emitted pollution are directly subjected to the total transported mass (fuel consumption and CO2 emission...). The construction and civil engineering sector values the ease of set ups with lighter weight handling machines while E&E takes into account the insulating properties of polymers and the possibilities of miniaturization.
To compete with metals, the main requirements for polymers are good dimensional stability, high mechanical performances, and temperature resistance. This is followed by the need for other properties such as better durability, FR and higher barrier performance notably to fuel. Lastly the breakthrough of bio-sourced polymers is a buoyant green point.
Many ways are being investigated - from polypropylene up to high performing engineering plastics reinforced with unidirectional or random glass or carbon fibres, plastic/metal hybrids, sandwich composites…
Metal replacement isn't a simple issue of polymer choice but must take into account complete solution systems including the plastic and its formulation, the obtained mechanical performances and collateral properties, the design, the processing method and the environmental impact.