Material guide
PI, polyimide
PI, polyimide. The plastic you reach for when the temperature is extreme and nothing else holds up. It keeps its strength and its shape in heat where almost every other plastic has already given up, and it insulates electrically into the bargain.
What it is
PI, polyimide, sits at the very top of the temperature scale among the plastics we carry. It is a material that keeps its mechanical strength, stiffness and dimensional stability at temperatures that make most other plastics soften or break down. Add good electrical insulation, low outgassing in vacuum and inherent flame resistance, and you see why PI ends up in the most demanding applications. It is also one of the most expensive and hardest to machine materials in the range, so it is chosen only when the requirements are extreme.
Properties
Among the highest there is in a moldable plastic, keeps its strength far up into the heat
Keeps its mechanical properties where other plastics soften
Good electrical insulation even at high temperature
Works in vacuum and space environments
Very low smoke generation without added flame retardant
Good dimensional stability even at high temperatures
Common applications
PI is used in environments no everyday plastic survives. Typical parts are insulators and components in power electronics, seals and wear parts in very hot processes, plus parts in semiconductor manufacturing, vacuum systems and aerospace applications. It also shows up as electrical insulation where both heat and voltage are high. When a designer faces a temperature requirement beyond PEEK and PAI, PI is often the only option left among the plastics.
Limitations
PI is one of the very most expensive materials in the range, and machining it is demanding, so it is never chosen for convenience. If your part gets by with PEEK, PAI or PEI there is no reason to pay for PI. The material can take up moisture, which matters with tight tolerances and in certain environments, something to allow for in the design. For purely chemical environments without extreme heat requirements there are more economical choices among the fluoropolymers. If you want to know whether PI is really needed for your case, get in touch before you order.
Our PI grades go to around 290 °C in continuous service, and the grades we have data for hold down toward -200 °C.
Grades and variants
PI comes in an unfilled grade and in filled variants. Which grade fits is governed by whether the part is mainly there to insulate, to slide or to hold its shape in extreme heat.
Base grade
- PI unfilled grade, the unmodified plastic for the highest heat resistance and electrical insulation.
Filled grades
- Graphite filled, for better sliding properties and abrasion resistance in bearings and wear parts.
- Other fillers, for adapted mechanical properties in demanding parts.
We will help you pick the right grade based on the requirements for insulation, sliding and heat resistance.
Machining
PI needs special tooling and experience, and the material is expensive enough that there is no room for mistakes. If your part gets by with PEEK or PAI, that is where you should land.
Formats we can supply
PI is available as sheets and round rods. You can see formats and dimensions in the range. Want a piece cut to size? Enter the dimensions in VisualCutter and you see the price right away.