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PET and PETG, a bad combination?

On Mar 19, 2018

Let’s face it, there are some things in this world that you should just never mix - like alcohol and bleach which can react to form poisonous compounds such as chloroform or hydrochloric acid. And then there are others that might be less dangerous but should still be avoided because they might cause potential problems – such as mixing different battery brands which can result in battery leakage and sub-optimal device performance because they likely contain different chemical compounds and varying voltages. But what about different types of resins?

ASTM International wrote the Resin Identification Code (RIC) to better help identify plastic. The RIC helps guide the plastics recycling value chain by providing information about the piece of plastic in question. The resin codes are the following:

Resin Code #1: Polyethylene terephthalate (PETE)
Resin Code #2: High density polyethylene (HDPE)
Resin Code #3: Polyvinyl chloride (V)
Resin Code #4: Low density polyethylene (LDPE)
Resin Code #5: Polypropylene (PP)
Resin Code #6: Polystyrene (PS)
Resin Code #7: Other, including materials made with more than one resin from categories 1-6

You might be wondering, what about PETG?

Plastic News states, “To the typical consumer, the difference between PET and glycol-modifies PET (PETG) is a simple letter. But to a polymer scientist with her molecular weight, there’s a huge difference. Especially when it comes to recycling.”

With something like recycling, one might assume it is fine to mix similar resins like PET and PETG. But, while the addition of glycol to PET makes it less brittle, it is believed that it also causes PETG to have a higher processing temperature than PET, creating challenges for recycling. In fact, according to Resource Recycling, “When they’re processed together, PETG melts and becomes sticky while PET remains solid. PETG sticks to PET chips and forms large clumps that pose processing problems.”

Because of this, California lawmakers recently revised their definition of polyethylene terephthalate (PET) to exclude the glycol-modified PETG, with a bill that could have impact well beyond the state’s borders – as many manufacturers sell their products to many states, not just California. With this legislation, PETG containers, such as some water bottles, will no longer qualify for the No. 1 resin code in California, but instead will likely be labeled No. 7 “other” plastics, making them more difficult, if not impossible, to recycle there. (Learn more about these codes in our previous blog, What do the latest ASTM revisions mean to you?)

While opponents of the bill such Eastman Chemical Co. and the Plastics Industry Association, agree that there is an issue when PET and PETG are mixed in the recycling stream, they claim that instead of changing the labeling and creating a double standard, technology already exists to adjust the sensitivity of the sorter at the beginning of the recycling process to differentiate between PET and PETG. However, recycling companies have not yet chosen not to invest in this equipment. Furthermore, after a recent review of the legislation, Eastman released their interpretation that medical device packaging will not be impacted by the law.

In addition, advocates of the bill have stated that they open to working with Eastman and the Plastics Industry Association to create a new resin code for PETG, so it can be more easily recycled in its own stream – another possible solution.

With these options, caveats, and several months until this legislation goes into effect, the final resolution remains to be seen.

That’s why it’s so important to work with thermoform manufacturers that can help you navigate this changing landscape as well as offer cost-effective alternative solutions with minimal impact on production. At TEQ, a good example of this is our sterile barrier system, TEQpropylene™, which offers sustainability, strength and clarity improvements over PETG. Plus, customers that move from using a material like PETG to TEQpropylene can achieve significant total package costs savings.

What about you? What are some solutions for “bad combinations” that have been developed in your business?

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