Guides / Materials
Engineering plastics on an unmanned aircraft, and where each one belongs
September 10, 2026
Most of a UAV is aluminium, and most of the plastic parts on it are there for one of three reasons: they must not conduct, they must not corrode, or they must slide. For the metals and the material callout checklist, see our guide to drone parts materials.
Picking the wrong polymer usually shows up as a part that grew, warped or softened in a place the designer never checked.
The four you will actually use
| Polymer | Density | Continuous temperature | Good at | Weak at |
|---|---|---|---|---|
| POM, acetal or Delrin | 1.41 g/cm3 | about 90 C | Dimensional stability, machining to tight tolerance, low friction | Softens and creeps with heat, poor adhesive bonding |
| PA66, nylon | 1.14 g/cm3 | about 100 C | Toughness, impact, cheap | Absorbs moisture and moves with it |
| PEEK | 1.32 g/cm3 | about 250 C | Heat, chemicals, stiffness for a polymer, insulation | Price, machining time |
| PTFE | 2.16 g/cm3 | about 260 C | Friction, chemicals, insulation | Very soft, creeps under any load |
Two rules of thumb carry most of the decisions. If it must hold a dimension, use POM. If it must survive heat, use PEEK.
Where each one lands on an airframe
POM is the default. Bushings, spacers, standoffs, skid blocks, isolator seats, small gears, non conductive washers and the sleeve that keeps an aluminium clamp off a carbon tube. It machines beautifully, holds tolerance and does not soak up water.
PA66 is for parts that get hit. Landing feet, bumper blocks, guards, latch bodies on a training aircraft. Accept that a nylon part in a humid climate is a few tenths of a millimetre bigger than the one you measured in the office.
PEEK is for the hot and the critical. Thermal breaks between a motor mount and a structure, insulators next to an ESC, seal carriers on a hybrid aircraft, connector bodies, anything sitting in an engine bay. It is also the choice when a plastic part has to hold a real load at temperature, because it keeps far more of its stiffness at 150 C than the others.
PTFE is for sliding and sealing only. Never for structure. It creeps under constant load at room temperature, which means a PTFE spacer under a bolted joint will slowly get thinner and the joint will loosen.
Machining differences that show up in the quote
Plastics are not automatically cheaper than aluminium to cut.
- Heat. Polymers carry heat away badly, so a cutter that dwells will melt the surface instead of cutting it. That means sharp tools, high speeds and often compressed air rather than flood coolant.
- Stress. Extruded stock has internal stress. Machine one side of a POM plate and it can bow. Precision parts get rough machined, annealed and finished, which is an extra step and a real cost.
- Tolerance. POM holds about ±0.05 mm comfortably on small features. PA66 is worse and drifts with humidity. PEEK holds well but likes an annealing step on anything with a close fit.
- Thermal expansion. All four move several times more than aluminium for the same temperature change. A POM part that fits an aluminium housing at 20 C will not fit the same way at 60 C. On close fits, say what temperature the fit applies at.
- Deburring. Plastics leave stringy burrs that take hand time. On a part with many small holes this can cost more than the cutting.
Specifying a plastic part so it arrives right
- Name the polymer and the grade, not just the family. Say PEEK, unfilled, or PEEK with 30 percent glass fill. They behave differently and cost differently.
- Say whether fillers are acceptable. Glass and carbon filled grades are stiffer and more stable. Carbon filled grades conduct, which defeats the purpose if the part is there to insulate.
- Give the fit temperature on anything close.
- Call out annealing if the part is precision, or say the tolerance and let the shop decide.
- Do not ask for anodise or passivation. It happens, and it tells the shop the drawing was copied from a metal part.
- Colour is the material. Natural POM is white, PEEK is tan, PTFE is white. If a colour matters, say so early, because black grades are separate stock.
When a plastic part is the wrong answer
- Where the load is structural and the part is thin. Aluminium is many times stiffer.
- Where the part is a heat path. Every polymer here is an insulator, which is the point when you want a thermal break and a disaster when you wanted a heat sink. See heat sinks and cold plates.
- Where a thread takes repeated assembly. Cut threads in plastic wear out. Use an insert.
- Where the part is near a motor and nobody measured the temperature. Measure it first, then pick.
We keep POM, PA66, PEEK and PTFE for UAV work alongside the metals on the materials list. Send the model and the working temperature, and the quote comes back within 24 business hours with the annealing decision already made.
Frequently asked questions
Is a plastic part always lighter than aluminium?
Yes by volume, roughly half the density or less, but not always by part. Plastics are far less stiff, so a plastic part often needs more material to hold the same shape under load. On a bracket carrying almost nothing, the saving is real.
Does nylon really absorb enough water to matter?
On a precision part, yes. PA66 can take up several percent by weight in humid conditions and grow noticeably with it. If the part has a tight fit or a bearing seat, use POM or PEEK instead.
Why is PEEK so expensive?
The raw polymer costs many times more than POM per kilogram and it machines slowly with annealing steps on precision parts. It is worth it where nothing else survives the temperature or the chemical exposure, and it is a waste anywhere else.
Need this part quoted?
Send the model and the quantity. Price and lead time come back within 24 business hours.