How to Choose the Right Engineering Plastic — Material Selection Guide

Step 1: Determine Service Temperature

Temperature is usually the first qualifying factor. Every plastic loses mechanical properties as temperature rises, and each has a ceiling beyond which it cannot be used.

Step 2: Chemical Environment

What chemicals will the part be exposed to? This quickly narrows the options:

Strong acids: PTFE, PVDF, PE (POM and PA are not resistant).

Strong alkalis: PA, PTFE, PE (POM degrades).

Solvents and hydrocarbons: POM, PTFE, PEEK (PA may weaken).

Fuels: POM is the best choice.

If chemical exposure is varied or unknown, PTFE and PEEK are the safest choices.

Step 3: Mechanical Loading

What type of loading will the part experience?

Static loading (continuous compression or tension): POM, PA66, PEEK. Be cautious with PTFE — it creeps under load.

Dynamic loading (impacts, vibration): PA is best due to its impact strength. PEEK also performs well.

Fatigue loading (repeated cycles): PA and POM withstand repeated stress well.

Step 4: Friction and Wear

If the part slides against another surface:

Lowest friction: PTFE (0.04–0.10), followed by POM (0.2–0.35) and PE-HD (0.2–0.3).

Best wear resistance: PA66, PEEK CF30, POM. PTFE wears quickly on its own, but fillers (carbon, glass fiber) improve this significantly.

Dry running: POM and PTFE work without lubrication. PA benefits from moisture or lubrication.

Step 5: Dimensional Stability and Moisture Sensitivity

If the part requires tight tolerances:

Best dimensional stability: POM — absorbs only 0.2% moisture, predictable and stable.

Note: PA absorbs 2–3% moisture, which changes dimensions by up to 1–2%. This must be accounted for in design and tolerances.

PEEK and PTFE are also exceptionally dimensionally stable (moisture absorption below 0.1–0.2%).

Step 6: Cost and Availability

The cheapest option is not always the best. A more expensive material can save money in the long run through longer service life, less maintenance and less downtime.

Quick Selection Chart

Temperature below 100 °C + good price? → POM or PA

Lowest possible friction? → PTFE

Aggressive chemicals? → PTFE or PVDF

Extreme temperature + strength? → PEEK

Impact strength + wear resistance? → PA66

Dimensional accuracy + dry conditions? → POM

Food/pharmaceutical industry? → POM-C, PE-HD, PTFE or PEEK

Summary

Material selection is always a compromise between different properties. There is no perfect material — but for nearly every application there is an optimal choice. Start with the most critical requirements (temperature, chemicals), narrow down the options, and from the remaining candidates select the one that best meets the mechanical and economic requirements.