Researchers Develops New Method To Convert Number Seven Plastics Into Valuable Products

A method for converting a widely discarded plastic to a resin used in 3D printing might enable for more efficient use of plastic waste.

A team of researchers from Washington State University found a simple and effective method for converting polylactic acid (PLA), a bio-based plastic used in items such as filament, plastic tableware, and food packaging, to a high-quality resin.

New method for recycling number seven plastic

(Photo : Marc Newberry/Unsplash)

The researchers discovered a way to instantly transform this into something stronger and better, and they hope that this will provide people with an incentive to upcycle this stuff rather than just throw it away, said Yu-Chung Chang, a postdoctoral researcher in the WSU School of Mechanical and Materials Engineering and a co-corresponding author on the work.

"We created stronger materials entirely from rubbish. We feel this is a fantastic opportunity," the scientist said as per ScienceDaily.

Every year, around 300,000 tons of PLA are manufactured, and its utilization is rapidly expanding.

Despite being bio-based, PLA, which is classified as a number seven plastic, does not degrade quickly. It can float for a year in either fresh or saline water without decaying.

It is also infrequently recycled since, like many plastics, when melted down and re-formed, it does not function as well as the original and loses value.

It's biodegradable and compostable, but research shows that it can take up to 100 years to decay in a landfill, according to Chang.

In actuality, it continues to pollute the environment.

The researchers want to ensure that when they start making PLA on a million-tonne scale, they will be prepared.

The researchers, led by Professor Jinwen Zhang of the School of Mechanical and Materials Engineering, developed a fast and catalyst-free method to recycle PLA, breaking the long chain of molecules down into simple monomers - the building blocks for many plastics - in their study, which was published in the journal Green Chemistry.

At mild temperatures, the full chemical process can be completed in about two days. Aminoethanol, the chemical used to break down the PLA, is likewise cheap.

"You have to tear down a Lego castle into bricks if you want to reassemble it into a vehicle," Chang explained.

The aminoethanol precision cuts the PLA down to a monomer, and once a monomer, the sky's the limit since it can be re-polymerized into something stronger.

The researchers reconstructed the PLA after breaking it down into its fundamental building parts, creating a sort of photo-curable liquid resin that is often used as printing "ink" for 3D printers.

When cured into plastic parts in a 3D printer, the product demonstrated equivalent or superior mechanical and thermal qualities than currently available resins.

While the study focused on PLA, the researchers want to adapt the findings to polyethylene terephthalate (PET), which is more prevalent than PLA, has a comparable chemical structure, and poses a larger waste problem.

Also Read: Recycled Plastics Harm Environment by Leaking Hazardous Chemicals, According to Experts

Number 7 plastics

Because the #7 category was created as a catch-all for polycarbonate (PC) and "other" plastics, reuse and recycling protocols are not standardized, as per Earth Easy.

The main concern with #7 plastics is the possibility of chemicals leaching into food or drink products packaged in polycarbonate containers made with BPA (Bisphenol A).

BPA is a recognized xenoestrogen and endocrine disruptor.

Baby bottles, sippy cups, water cooler bottles, and automotive parts are all made from number 7 plastics.

BPA is discovered in polycarbonate plastic food containers, which are frequently labeled with the initials "PC" on the bottom by recycling label #7.

To replace polycarbonates, a new generation of biodegradable plastics manufactured from bio-based polymers such as corn starch is being developed.

These are also listed in category #7, which might lead to consumer confusion. These compostable plastics bear the initials "PLA" near the recycling symbol on the bottom. Some may also use the term "compostable."

#7 plastics are not for reuse unless they have the PLA compostable coding. When possible, avoid using #7 plastics, especially for children's meals. Plastics with the recycling labels #1, #2, and #4 on the bottom are safer and contain no BPA.

PLA labeled plastics should be composted rather than recycled since PLA biodegradable plastics are not recyclable.