Can Engineering Thermoplastics Replace Metal?

In 2013, Piotr Kamiński of Danje-Polymer published an article in “PlastNews” titled “Tworzywo sztuczne – młodszy brat metalu” (“Plastic: Metal’s Younger Brother”). He described materials capable of dissipating electrostatic charge, shielding electromagnetic interference, transferring heat and performing in demanding structural components. More than a decade later, the question he raised remains relevant: when can a thermoplastic take on the role of a metal component?

The answer depends on what the finished part needs to do. Lower weight or the ability to mould a complex shape is not enough. The material must meet electrical, thermal and mechanical requirements under real operating conditions, and the part must be designed around the properties of the selected grade.

When charge control or electronics protection matters

Most standard plastics are good electrical insulators. With appropriate additives, however, thermoplastics can be made antistatic, static dissipative, electrically conductive or suitable for electromagnetic interference (EMI) shielding.

These are different jobs. Reducing charge build-up on a surface, providing a controlled path for charge dissipation and shielding electronics call for different material properties and often different part designs. The LNP™ STAT-LOY™, STAT-KON™ and FARADEX™ families, for example, address different needs in this area. In FARADEX™ compounds, a network of conductive fibres enables EMI/RFI shielding in appropriately designed parts.

What should you verify? The required resistance or resistivity, the test conditions, shielding effectiveness over the relevant frequency range, and the effects of geometry, joints and operating conditions. For equipment intended for potentially explosive atmospheres, material selection is only one part of the safety assessment of the finished product.

When heat needs a path out but electricity must stay insulated

Piotr Kamiński’s article used LED luminaires as an example of how thermal management could create new opportunities for thermoplastics. It remains a relevant challenge. Heat generated by electronics must be transferred away while maintaining the required electrical insulation and allowing freedom in enclosure design.

Thermally conductive plastics include both electrically insulating and electrically conductive grades. The LNP™ KONDUIT™ family contains materials designed for such applications; the manufacturer specifies thermal conductivity in the range of approximately 1–18 W/(m·K), depending on the grade. This is not a universal value for every thermally conductive plastic.

What should you verify? The thermal conductivity of the specific grade and the direction in which it was measured, the required electrical insulation, operating temperature, flammability requirements and heat dissipation in the finished part. When comparing the design with metal, consider the whole component: shape, wall thickness, heat-transfer surface and mounting method.

When weight, durability and design freedom count

Replacing metal with a thermoplastic may reduce part weight, combine several functions in one moulded component or reduce assembly steps. This applies to selected uses, not to every metal part.

Depending on the requirements, designers may consider fibre-reinforced plastics, high-heat materials such as PEI, or grades modified to manage friction and wear. The LNP™ THERMOCOMP™ and LNP™ LUBRICOMP™ families, for example, offer different ways to tailor a part’s properties to mechanical loads and contact with other surfaces.

What should you verify? Short- and long-term loads, creep, fatigue, temperature and operating environment, dimensional tolerances and any industry-specific requirements. A test result for one grade or one part should not be applied to an entire material family.

The same idea, with a more precise selection process

The title of the 2013 article still invites engineers to consider new solutions. In some designs, a thermoplastic can replace metal; in others, the two work together in one device. The function of the part and the complete set of requirements determine the material choice. Successful implementation also depends on selecting a specific grade and validating the prototype.

At Danje-Polymer, we help turn application requirements into potential material options and identify the properties worth checking before implementation. If you are considering a material change, tell us about the application, operating conditions and the key requirements for your part.

This article refers to Piotr Kamiński’s “Tworzywo sztuczne – młodszy brat metalu”, published in “PlastNews”, issue 1/2013. It is a contemporary follow-up to the original article, not a reprint.