Temperature resistance of plastics

The temperature resistance of plastics is a central selection criterion in the design of technical components. Whether in mechanical engineering, electrical engineering, medical technology or vehicle construction – thermal loads help determine which material is suitable for a particular application. This is because plastics react sensitively to temperature changes: they can become soft, deform, lose their strength or become brittle. It is therefore crucial to check already during the development phase which materials reliably and permanently cover the required temperature range.

Unlike metals, many plastics are temperature-dependent in their mechanical and chemical stability. The challenge is to find a material that fulfils its function even at permanently high or low temperatures. In this article you will receive a comprehensive overview of temperature-resistant plastics, typical characteristic values and application limits as well as recommendations for selecting suitable materials.

What does temperature resistance mean for plastics?

Temperature resistance is understood as the ability of a plastic to maintain its mechanical, chemical and physical properties at high or low temperatures. Unlike metals, which exhibit relatively stable properties over a large temperature range, plastics often show a pronounced temperature-dependent behaviour. This property is not to be equated with the melting temperature, but rather describes the functional application range of a material under thermal load.

Temperature resistance can be described by various characteristic values, such as the continuous service temperature, the Vicat softening temperature or the glass transition temperature. Depending on the type of plastic (amorphous or semi-crystalline), these values vary greatly. Particularly for safety-relevant or long-term stressed components, it is therefore important to know the exact application conditions and to compare them with the material data.

Typical values for guidance:

• Short-term temperature load: up to 250 °C (e.g. with polyimide)
• Continuous service temperature: usually between −20 °C and +150 °C
• Cold resistance: some plastics can be used down to −200 °C (e.g. PTFE)

Influence of temperature on plastic properties

Embrittlement in the cold

Many amorphous plastics lose their toughness at low temperatures. Molecular mobility decreases, which leads to increased brittleness and thus to a higher risk of fracture under mechanical stress. Plastics for applications below zero degrees should therefore be selected carefully.

Softening in heat

If the temperature rises above the glass transition temperature, thermoplastics become soft and lose their dimensional stability. This can lead to permanent deformation, sink marks or dimensional inaccuracies – particularly in components under mechanical load.

Creep behaviour

Under sustained application of force and simultaneously elevated temperature, many plastics exhibit creep behaviour. This means that they deform slowly but permanently under constant load. This is particularly critical for load-bearing or precisely fitting components.

Changed electrical properties

As temperature increases, the electrical properties of many plastics also change. Insulating capacity decreases, the dielectric constant can increase and leakage currents or flashovers can occur. This must be observed above all in electrical engineering.

Thermal characteristic values at a glance

Characteristic value	Meaning	Unit
Service temperature	Temperature range for continuous application	°C
Melting temperature	Point at which the plastic melts (in semi-crystalline thermoplastics)	°C
Glass transition temperature (Tg)	Temperature from which amorphous thermoplastics become soft	°C
Heat deflection temperature (Vicat)	Resistance to deformation under load	°C
Coefficient of thermal expansion	Change in length per degree of temperature change	1/K

High-temperature plastics in comparison

Some plastics are distinguished by particularly high temperature resistance. Here is a selection of typical representatives:

Plastic	Continuous service temperature	Short-term usable up to	Remark
PTFE	approx. 260 °C	over 300 °C	Very resistant to chemicals, non-flammable
PEEK	approx. 250 °C	up to 300 °C	High-strength, for aerospace and medical technology
Polyimide	approx. 250 °C	up to 400 °C	Extremely temperature-stable, expensive
PPS	approx. 220 °C	up to 270 °C	Flame-retardant, good chemical resistance
PEI	approx. 170 °C	up to 200 °C	Good electrical properties

Selection according to temperature requirements

When selecting a temperature-resistant plastic, various factors play a role:

• Temperature profile of the application (continuous vs. short-term)
• Mechanical loads under temperature
• Contact with chemicals, UV radiation or friction
• Shaping and manufacturing technologies (e.g. injection moulding, milling)

For temperatures up to approx. 100 °C, modified standard plastics (e.g. PC, PA6) are often sufficient. In the range 100–200 °C, engineering plastics such as PSU, PBT or PPS are used. Above 200 °C, high-performance plastics such as PEEK, PI or PTFE are required.

Typical applications of temperature-resistant plastics

• Automotive engineering: bearing shells, seals, sensor covers
• Electrical engineering: insulators, plug connections, coil formers
• Medical technology: sterilisable components made of PEEK or PPSU
• Aerospace: structural parts made of PI, PEEK or PEI
• Food industry: heat-resistant conveyor belts or plain bearings

Conclusion

The temperature resistance of plastics is not a static value, but a dynamic interplay of material structure, duration of use and environmental influences. Anyone designing thermally stressed plastic components should therefore not only pay attention to the pure temperature specification, but also keep an eye on creep behaviour, chemical influences and mechanical load. With the right choice of material, the service life and safety of components can be decisively extended.

FAQ on the temperature resistance of plastics

Which plastics withstand high temperatures? High-temperature plastics such as PEEK, polyimide (PI), PTFE and PPS withstand temperatures above 200 °C permanently.

What is the glass transition temperature? The glass transition temperature is the point at which amorphous plastics change from a solid to a rubber-like state.

How do I find the right plastic for hot applications? The selection depends on temperature, duration of load, mechanical stress and chemical requirements. A material data sheet helps with the decision.

Can plastics become toxic in heat? Some plastics decompose when overheated and can then release gases harmful to health. Compliance with the recommended service temperature is therefore important.

Are there cold-resistant plastics? Yes, for example PTFE, POM or UHMW-PE retain their properties even at very low temperatures.