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PEI – Extruding The High-Performance Polymer

PEI, Polyetherimide, is one of the more rare polymers we have tested here at 3devo. That, however, does not mean it is any less useful. This high performance engineering thermoplastic, usually with an amber to transparent colour, makes a great name for itself in various high-demanding applications. It can often replace metal or other strong substances thanks to its impressive chemical and mechanical properties, but how well does it extrude? In this article we will make a brief overview of PEI as well as our extrusion tests for this strong polymer.

Filament Summary

PEI’s characteristics include extreme rigidity, high strength (even at elevated temperatures), long term heat resistance, dimensional stability and good electrical properties. It is easy to spot due to its light amber colour (unfilled) and is usually semi-transparent. Like other amorphous, high temperature resins, PEI has outstanding dimensional stability and is inherently flame retardant.

PEI does resist chemicals, such as hydrocarbons, alcohols and halogenated solvents. Creep resistance over the long term allows PEI to replace metal and other materials in many structural applications. It is also widely used in electronics because of its good arc resistance and dielectric constant. Furhermore, PEI is UFDA/USDA and USP class VI compliant.

Applications

PEI used in vape mouthpieces (left) to plastic manifolds (right) via Carville Plastics
  • Reusable machined components
  • Aircraft/Automotive instrumentation
  • Plastic Manifolds
  • Electrical insulators
  • Electrical component housings

Advantages

  • Great thermal stability (continuous use temperature of 365F/180° C)
  • High strength
  • Continuous rigidity and strength to 340F (170°C)
  • Dimensionally stable
  • Excellent flame and heat resistance (UL 94 V-0 rated)
  • Consistent dielectric properties over a range of frequencies
  • Good acid resistance
  • High resistance to autoclave sanitizing
  • Low moisture absorption
  • Can withstand steam autoclaving
  • Inherently flame retardant
  • Certified Grades for food-contact and bio-compatibility applications

Disadvantages

  • Can be expensive
  • Not a lot of colour choices (amber or sometimes transparent)

Extruding PEI (ULTEM 1010 Resin)

Here at 3devo we were able to acquire some PEI for extrusion tests (Ultem 1010 Resin was used). Because of its high strength factors we were interested to see what the results would be. Below is an overview of the whole process, however, for a more detailed report please contact us via the sales contact page.

Preparation

PEI resin (left) and adding it into the hopper (right)

First cleaning of the extruder had to take place. Using ASACLEAN™ GL2, followed by ASACLEAN™ PX2, we were able to clean the device to prevent any impurities impacting the results. Once both materials had run through the device in order to properly clean it, the heaters were all set to the same temperature (160 °C).

Observation Indicators

There are three important things to look out for when extruding new filament for the first time:

  • How does the filament look? Are there any signs of bubbles/holes, die lines, weld
    lines, melt fracture or warpage?
  • Is the flow similar to that of standard PLA (when using the same rpm)?
  • Is it possible to pull the material without any trouble (the material does not stick to
    the puller wheel and does not break as a result of the force of the puller)?

Extrusion Summary

Extruding PEI (left) and the results (right)

After multiple tests, we concluded that PEI is able to be successfully extruded with the NEXT. The tests we ran determined that PEI should be extruded below 370 °C (but not too low) in order to prevent bubbles and holes from forming, and that proper cleaning methods should be used in order to determine the best results.

Conclusion

In the end, PEI was a very interesting polymer to test out compared to other ones we have tested in the past. Its high strength, rigidity and thermal stability meant that a lot of care had to be taken when running the tests. PEI though is a great filament and very useful, especially in aerospace and automotive applications.

Testing PAEK – Is It Any Good?

Here at 3Devo, we really enjoying testing a variety of different filaments. Last week we were about to test some PAEK. As you may or may not know, PAEK is a family of semi-crystalline thermoplastics with high-temperature stability and high mechanical strength. We were lucky enough to test some AvaSpire AV-621 from Solvay (provided by ALBIS PLASTIQUE France). Catchy name, but is it any good? This article will cover all you need to know about PAEK, and how it performed in our tests.

General Information

Image 3devo – PAEK material provided by ALBIS Plastique France

As mentioned PAEK, or polyaryletherketone, is a family of semi-crystalline thermoplastics. In this family you will find:

  • Polyetherketone (PEK)
  • Polyetheretherketone (PEEK)
  • Polyetherketoneketone (PEKK)
  • Polyetheretherketoneketone (PEEKK)
  • Polyetherketoneetherketoneketone (PEKEKK)

Polyaryletherketone (PAEK) was first prepared in the early 1970s, but results and the overall process was somewhat limited. PEEK was the first thermoplastic to go large scale in 1977, where ICI used polyetherification reactions to create the polymer. In 1981, Victrex of Lancashire, England, introduced PEEK resins commercially. Next came PEK, introduced by BASF AG, the large German plastics company, which attempted to gain the total market share, eventually stopping all production of PEKEKK resins. This left Victrex as the only supplier of PEK resins in the world.

In the end, PEEK’s growth rates started to soar, mainly due to its high mechanical strength and chemical resistance. From vehicles, to aircrafts, to most electronics and medical applications, more and more suppliers started to enter the market. These suppliers include:

Below is a list of some of the advantages and disadvantages of using PAEK:

Advantages

  • Highly fire-resistant
  • Good chemical resistance
  • Can be used for high temperature applications
  • Excellent mechanical and dielectric properties

Disadvantages

  • Relatively high cost material
  • Anisotropic
  • High temperature molding and extrusion required

Tests

In our first attempt to create PAEK filament we used the AV-621 NT grade produced by AvaSpire with a melting point of 340°C, which we pre-dried at 150°C for 4 hours. The first step in the extrusion process was using PX2 cleaning purge (with a temperature range of 280-420°C) as a transition material, in order to be able to raise the temperature of all heaters to 380°C.

paek-test-1
Filling up the NEXT TEST Advanced Extruder, then running the test

The first thing we noticed while extruding with an overall temperature of 380°C, was the large amount of air bubbles in the filament. This could mean two things, either the granulate was not dry enough, or the overall temperature is too high. Lowering the overall temperature by 10°C improved the quality a lot, but now we faced nozzle lip buildup as you can see in the picture below:

paek-test-3
Nozzle lip buildup

Some polymers tend to have this problem, and it causes major surface roughness of the filament. In this case, the buildup was reduced by increasing the temperature of the front heater.

paek-test-4
A little rough around the edges

In the end we managed to create a spool of PAEK with a filament thickness of 1.75mm, but the surface of the filament was still on the rough side. This means we will keep on looking for better settings of the Next Advanced Extruder, but at least the machine has now proved its ability to create PAEK filament. This adds up in the list of successfully tested high-end polymers, along with materials such as PEEK and PEKK.