Engineering plastics at low temperatures

Engineering plastics are indispensable in modern industry. They offer a combination of lightweight construction, chemical resistance and cost-efficient processing. But when it comes to extreme operating conditions, in particular low temperatures below -40 °C, designers and material experts face particular challenges.

In applications such as industrial refrigeration, cryogenics, outdoor use in polar regions or in aerospace, conventional plastics reach their physical limits. Here it is crucial to choose materials that remain dimensionally stable, impact-resistant and resistant even in severe cold. This article examines which properties engineering plastics exhibit at low temperatures, which risks exist and which materials are particularly suitable.

Challenges at low temperatures

Falling temperatures significantly influence the physical properties of plastics. Conditions become particularly critical below the so-called glass transition temperature. In this range, many plastics lose their elasticity and become brittle, which can lead to cracking or mechanical failure.

For applications below -40 °C, it is therefore essential to understand how the molecular structure of a plastic behaves. Many materials harden considerably, lose their toughness and break more quickly under load. The risk is particularly high under dynamic stresses such as impacts, shocks or vibrations. In addition, thermal expansion is reduced, which can lead to stresses in assemblies.

Media resistance also plays a role: refrigerants, oils or other fluids used at low temperatures can additionally attack certain plastics chemically. For a material to function reliably under these conditions, all influencing factors must be taken into account – from mechanical load and chemical influences through to possible UV exposure outdoors.

Critical material changes below -40 °C:

• Embrittlement due to glass transition
• Cracks under impact load
• Restriction of thermal expansion
• Change in friction behaviour

Important properties of engineering plastics in cold conditions

A plastic for low temperatures must:

• retain high impact resistance even under the influence of cold,
• remain dimensionally stable,
• be dimensionally accurate and exhibit low changes in length,
• be resistant to media (e.g. against refrigerants),
• exhibit good insulating properties if electrical components are integrated.

Suitable engineering plastics for low-temperature applications

Plastic	Temperature resistance	Properties in cold conditions	Typical applications
PE-UHMW	down to -200 °C	Very high impact resistance, wear-resistant	Frozen food logistics, skids, plain bearings
PTFE	down to -200 °C	Chemical-resistant, low-temperature-resistant	Seals, bearings, chemical plants
PA6	down to -40 °C	Good strength, borderline at -40 °C	Outdoor technology, vehicle construction
POM-C	down to -50 °C	Good machinability, low water absorption	Refrigeration machines, insulating elements
PE-HD	down to -50 °C	Weather-resistant, impact-resistant	Storage tanks, pipe systems
PVDF	down to -60 °C	Chemical-resistant, good strength	Process plants, cryogenics

Application examples

Refrigeration technology

In industrial refrigeration technology, for example PTFE or POM components are used in compressors, valves or refrigerant distributors. Here, in addition to temperature resistance, high media resistance is also required.

Outdoor applications

Plastics such as PE-HD or PA6 are used in snow blowers, outdoor housings or transport packaging for arctic conditions. UV stability and impact resistance play a major role here.

Aerospace

In aerospace, high-performance plastics such as PEEK or PTFE are used. Here the materials must withstand temperature fluctuations from -150 to +200 °C without damage and at the same time be weight-saving.

Selection criteria for the right plastic

When selecting a material, the following criteria should be taken into account:

• minimum temperature in the area of application
• mechanical load (static/dynamic)
• contact with media (e.g. refrigerants, water)
• electrical requirements (insulation, conductivity)
• machinability and availability

Conclusion

Low-temperature applications place particular demands on plastics. While many standard plastics become brittle or fail mechanically at temperatures below -40 °C, specialised engineering plastics offer a reliable solution. Materials such as PTFE, PE-UHMW or PVDF are distinguished by high impact resistance, good chemical resistance and stable mechanical properties even at extreme sub-zero temperatures. For engineers and designers, it is therefore essential when selecting a material to consider not only the service temperature but also factors such as media contact, mechanical loads and environmental influences. Only in this way can durable and safe components be realised for use in cold, frost and cryogenic environments.

FAQ

Which plastics withstand temperatures below -50 °C? PTFE, PE-UHMW and PVDF are suitable for very low temperatures. They remain tough and dimensionally stable even below -100 °C.

What happens to PA6 in severe cold? PA6 can become brittle at temperatures below -40 °C and then loses its impact resistance. It is therefore only suitable to a limited extent.

Which industries use plastics at sub-zero temperatures? Typical examples are refrigeration technology, outdoor equipment, food processing, aerospace, deep-sea technology and laboratory technology.