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PET Recycling – From Bottle to Filament

Recycling. A word often related to large companies receiving tons and tons of paper or plastic in an effort to reduce our carbon footprint. However if we look at plastic bottles for instance, humans buy a million plastic bottles per minute, and 91% of all plastic is not recycled. This article is going to cover what makes plastic recycling so important, how to recycle PET and the future of recycling in 3D printing.

What is PET Recycling?

Focusing on plastic bottles here, they have one huge advantage – unlimited recycling potential. PET is one of the few polymers that can be recycled into the same form over and over again. Think of it as a closed-loop recycling solution.

PET recycling loop
The “closed-loop” of PET recycling. Image via PETCO

Recycled PET, or rPET, can be used to make many new products. This can range from clothing, automotive parts, packaging as well as bottles for food/non-food products. Depending on the application required, rPET will be blended with the original PET.

What Are The Uses of Recycled PET (rPET)?

As mentioned above, rPET has many great uses, which includes:

  • Food containers
  • Polyester carpet fiber
  • Fabric for T-shirts
  • Athletic shoes
  • Luggage and upholstery
  • Sweaters and fiberfill for sleeping bags and winter coats
  • Industrial strapping
  • Sheet and film
  • Automotive parts
  • New PET containers
Some recycled PET products

Using rPET in place of the normal or virgin PET has substantial environmental impacts as well as reducing overall energy consumption.

Creating Our Own Filament from Plastic Bottles

Now that we’ve covered the background of recycling PET, how exactly does one go about doing the actual recycling? The one method is simply going to your local recycling company and dumping your plastic waste there, or having it picked up at home if that company provides a pick-up functionality. The other method though is a bit more rewarding – doing it yourself.

We wanted to test of normal plastic bottles can be turned into 3D printing filament. The following is a quick summary of our tests to turn around 30 bottles into filament.

  • Water bottles were collected, cleaned (properly) and any external caps or seals were also removed
  • The bottles were then vacuum sealed and heated to reduce their size
  • Once cooled the bottles were cut into smaller chunks with a saw and a pair of scissors
  • After that, the pieces were shredded into tiny pieces using our SHR3D IT
  • The pieces were then dried at a temperature of 160°C for 4 hours
  • The PET was then fed into our Next filament extruder
  • After multiple tests at different nozzle diameters and temperatures, our team ended up with a great result of PET filament
PET Filament Final Result
Final results of the filament

If you’d like to read the complete test and the different results, you can find the document here.

The Future of Plastic Recycling in 3D Printing

The biggest issue that faces 3D printing recycled filament – dirt. With the above experiment, just cleaning those bottles took a great deal of effort. Now imagine doing it with tons of plastic, often coming from dumps that have been contaminated all forms of impurities.

Also, one has to take note that different types of plastic produce different types of filament. High-density polyethylene — shampoo bottles, for example — are relatively easy to convert into filament, but it’s difficult to print with because it shrinks more than other plastics as it cools. On the other hand, PET, prints well but is brittle, making it difficult to spool as filament.

Recently, we saw the US Department of Defense (DoD) is exploring 3D printing feedstock made from plastic containers that have been left on the battlefield, which can hopefully be reproduced in other government sectors. There’s also Ethical Filament, a company focused on promoting the concept of recycling to produce ethical 3D printing filament that is sold to improve the livelihoods of waste pickers and their communities worldwide. Then there’s the Perpetual Plastic Project (PPP), which is an installation which can directly recycle old plastic drinking cups into 3D printing gadgets as well as other plastic products if needed.

While there is more and more aware of using recycled filament for 3D printing, we still have a long way to go. Hopefully, with the rise in 3D printing over the last few years, more emphasis is being placed on plastic recycling.

 

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.
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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.

Year and a Half Later – Setting the standard with PEEK

Year and a Half Later – Setting the standard with PEEK
A year and a half ago, we began testing the prototype of what is today referred to as the Next 1.0 Advanced Level desktop filament extruder.
Taking forward the same commitment to quality and innovation, we focused on our next experiment – working with a semi-crystalline thermoplastic with mechanical and chemical properties ideal for sustaining high temperatures. This thermoplastic is known as PEEK (Polyether Ether Ketone).
Working with PEEK has presented interesting challenges, chief among which involved extruding it in the correct temperature range, while factoring in internal pressure, and without affecting the material’s crystallinity. It has been a good start, and our first trials turned out to be easier than expected.
But first, a bit about PEEK. And its key applications.

PEEK test result 1.75mm 3devo filament
PEEK test result 1.75mm 3devo filament – done by Apium Additive Technologies GmbH http://apiumtec.com/en/3d-printer/

PEEK finds its main uses in the Aerospace, Automotive and Medical industries.

Aerospace industry: Being strong, lightweight, and durable in a wide range of temperatures, PEEK is evolving into a popular choice of material in the aerospace industry. Its low price point does not hurt either.

Aerospace part
Aerospace part
Source: www.roboze.com

Automotive industry: Besides the primary advantages of its high strength (safety), low weight, and durability in a wide range of temperatures, PEEK is also energy efficient and has the intrinsic ability to reduce vibrations. This makes it a perfect fit for the fast developing automotive industry.

Gear Pump Source: www.Apiumtec.com
Gear Pump
Source: http://apiumtec.com/en/3d-printer/

Medical industry: 3D printing has already established itself as an invaluable asset to the medical and dental industries, bringing a whole new level of freedom and accuracy to the process of printing unique parts and components. PEEK (or PEKK for dental industry) extends the scope of 3D printing, having similar properties as the human bone, and thus being one of the few materials that the body does not resist.

Implants Source: www.pkm.kit.edu
Implants
Source: www.pkm.kit.edu

Recent PEEK tests with the Next 1.0 Advanced Level desktop filament extruder
Switching from PLA to PEEK presented an unique challenge: building up the temperature inside the Advanced Level extruder to PEEK’s high melting point of 343 degrees.
We went about it in phases, using 2 cleaning compounds as transition materials. First, we slowly raised the temperature from 170 to 300 degrees with the first transition material. Once temperatures had crossed 300 degrees, we switched to the second transition material, and worked on reaching 390 degrees. This was the final stage in our trial, where we could proceed to extrude PEEK.
Because of PEEK’s steady flow and relatively quick cooling properties, extruding it to the desired thickness (2.85mm or 1.75mm) was easier than expected. Winding it on a spool was a different ballgame, though. Due to the strength of the material we had to tape the first part of the filament on the spool, so as to wind it correctly and prevent it from popping out of the spool.

3devo PEEK Filament 2.85mm
3devo PEEK Filament 2.85mm

Transition materials and PEEK
The transition material played a key role throughout our PEEK extrusion process. We first mixed the PEEK with the transition material, and then gradually lowered the temperature range while increasing the amount of transition material in the mix.

PEEK and purging compound @3devo
PEEK and purging compound @3devo

Phase 1

Image: 3devo BV - phase 1 extruding PEEK
Image: 3devo BV – phase 1 extruding PEEK

Phase 2

Image: 3devo BV - phase 2 extruding PEEK
Image: 3devo BV – phase 2 extruding PEEK

Extruding your own PEEK – The main advantages
Buying PEEK granulate will only set you back by around 100 Euros per kg, as opposed to a filament spool that will cost you to the tune of 1000 Euros per spool.
In addition to this, you can try creating custom composites with PEEK granules, by adding in different materials such as carbon fiber.

Do you have one of our Advanced Level extruders?
Contact sales@3devo.com for the profile settings to start extruding PEEK.

ABS vs PLA Filament – What’s The Difference?

Like it or not, you simply can’t go out and start 3D printing without some prior filament knowledge. No matter how impressive your 3D printer is, choosing the wrong filament could make your next print look like it escaped from Chernobyl. Therefore in this article I’ll be giving you the very basics of printing with the two most popular filament types – ABS and PLA.

What is a Filament Extruder?

What are we building?

3devo is developing a filament extruder. This is a machine that processes plastic pellets into a plastic wire. This plastic wire (filament) is mainly used as printing material for 3D printers, in a manner similar to an ink cartridge being used by a regular printer.

Overall, filament is extruded on an industrial scale. We developed a product that makes the quality of industrial extrusion setups within everyone’s reach. Taking the systems and knowledge of industrial machinery and reducing the size to fit a consumer desktop model in such a way that each user can have his own professional filament extruder. This means scaling down, simplifying, automating and making the extrusion process more consumer-friendly.

For more information check our product page!