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Polymaker and Covestro Make 3D Printing Filament from Water Bottles

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3D printing filament firm Polymaker is working with Covestro to make Polymaker PC-r, a recycled polycarbonate. The polycarbonate is sourced from huge 19-liter bottles made by Nongfu Spring. These bottles are used repeatedly for residential and office water throughout China. Covestro started a project in 2020 to work with Nongfu to recycle a million of the water bottles per year.

Some virgin material is required for the production of new filament, but most of it comes from recycled bottles. In turn, the resulting material the “Blue Angel and EPEAT seal.”

Covestro noted, “The fact that the waste comes from one single source is an advantage. This means that no prior sorting and identification of the plastics is necessary. The plastic waste is quite pure and can be recycled in a cost-effective manner. In addition, it is available in sufficient quantities. In China, large-volume water bottles are widespread in private households and public places. These are collected and refilled again and again before finally discarded and sent for recycling.”

Compared to single use plastic bottles, this is a lot more sustainable. There is another advantage to this as well: the MFI (melt flow index) is known and constant, which means that it is easier to compound the material, extrude it into filament, and print it. In the case of these bottles, collection is also known and easy, since partners often perform this work when bottles are exchanged, meaning that you don’t have to fish it from the trash.

Covestro also says that to print the polycarbonate well without warping, constant chamber temperatures are necessary. This was tested out on a FUNMAT PRO 410 from INTAMSYS. When made in this way, “the test scores show good values for tensile strength, Young’s modulus, flexural strength, and flexural modulus, which were slightly higher than standard polycarbonate.”

This is a lovely example of companies working together toward more circular practices. I’m usually extremely cautious with these kinds of projects and announcements. There is a lot of greenwash and over-claim in this area. In this case, it seems like it is a solid implementation that is also realistic. By working with a traceable container whose life and condition can be approximated and by working with a substance whose values are known makes it much easier to do something like this well.

Meanwhile by working directly with the water company, future bottle designs can be optimized for recycling by using a different glue for labels or dispensing with them entirely, for example. The removal of rings and caps can also be optimized. In this case there is also little chance of the polymer being contaminated or degraded beyond its useful life. They know exactly when the bottle was made, how long it was used, and how many cycles it was used for. In post-consumer waste, there is usually a worry as to what kind of substances the polymer has come into contact with or how it was treated previously. This is all avoided by this approach.

If we go further still, then Covestro could see itself as a custodian of this material and, for example, plan for its traceable use for eight cycles as a consumer water bottle and then allow for a double recycling stint as a consumer electronics housing before turning it into a 3D printing material. If a QR code could then always identify the material, as well as when it was made and what additives are in it, then it could be managed for years. Rather than pitch some granulate over the fence, Covestro would be managing a polymer for decades in the most sustainable fit-for-purpose way. I applaud things like these and think we should have a lot more initiatives like this one.

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