A novel PET-like plastic is made from non-edible plant parts

It is easy to recycle too.
Ameya Paleja
A 3D printed leaf made with the new bioplasticAlain Herzog/EPFL

Researchers at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have developed plastic from non-edible parts of the plant, a university press release said. This new plastic has properties like polyethylene terephthalate (PET), a commonly used plastic, making it a promising candidate for its replacement. 

The United Nations Environment Programme (UNEP) estimates that a million plastic bottles are purchased every minute in the world today, while five trillion plastic bags are used worldwide every year. Plastics are so ubiquitous in our environments now that they have started their own marine microbial habitat called the "plastisphere" and have already become part of the fossil records of the current geological era.

According to UNEP estimates, 36 percent of all plastics produced are used for food packaging, which also includes single-use products, most of which end up in landfills. 98 percent of single-use plastic products are made using fossil fuels, which means that the production, use, and disposal of these plastics all generate greenhouse emissions, making plastic reduction a key component in fighting climate change

Why do we love plastic so much? 

One of the prime reasons why plastic is used almost everywhere is its versatility. From being thermostable to being able to withstand mechanical forces, plastic can truly stand the test of time. Add to the mix the benefits of easy processing and the low cost of manufacture, it is not difficult to imagine why plastic usage has exploded in the past few decades. 

Many plastic alternates have been researched and developed, but they have failed to tick all the boxes when it comes to the benefits of conventional plastics until now. A team of researchers led by Professor Jeremy Luterbacher at EPFL has now found a method to manufacture plant-based plastic that not only has the benefits of conventional plastic but can also be naturally recycled.

How did the researchers convert plant parts to plastic? 

In 2016, Luterbacher and his team made a groundbreaking discovery when they found that adding an aldehyde, an organic compound, to plant material stabilized a certain fraction of the plant, paving the way for its extraction.

Now in recently published findings, Luterbacher's team has switched the aldehyde used in the process to extract a plastic precursor from non-edible plant parts. Instead of using formaldehyde, the commonly known aldehyde, the researchers used glyoxylic acid,  which then "clip(s) 'sticky' groups onto both sides of the sugar molecules," making them building blocks of plastic. Using the technique, the researchers were able to convert 25 percent of agricultural waste into plastic, the press release said. 

The researchers have found this newly developed plastic can be used in a wide spectrum of applications, ranging from textiles to medicine and even electronics. The researchers have used this plastic to make food packaging films as well as converted them into filaments that can be used in 3D printing

"What makes the plastic unique is the presence of the intact sugar structure," said Luterbacher in the press release. "This makes it incredibly easy to make because you don't have to modify what nature gives you, and simple to degrade because it can go back to a molecule that is already abundant in nature."

The findings were published in the journal Nature

Abstract:
The development of sustainable plastics from abundant renewable feedstocks has been limited by the complexity and efficiency of their production, as well as their lack of competitive material properties. Here we demonstrate the direct transformation of the hemicellulosic fraction of non-edible biomass into a tricyclic diester plastic precursor at 83% yield (95% from commercial xylose) during integrated plant fractionation with glyoxylic acid. Melt polycondensation of the resulting diester with a range of aliphatic diols led to amorphous polyesters (Mn = 30–60 kDa) with high glass transition temperatures (72–100 °C), tough mechanical properties (ultimate tensile strengths of 63–77 MPa, tensile moduli of 2,000–2,500 MPa and elongations at break of 50–80%) and strong gas barriers (oxygen transmission rates (100 µm) of 11–24 cc m−2 day−1 bar−1 and water vapour transmission rates (100 µm) of 25–36 g m−2 day−1) that could be processed by injection moulding, thermoforming, twin-screw extrusion and three-dimensional printing. Although standardized biodegradation studies still need to be performed, the inherently degradable nature of these materials facilitated their chemical recycling via methanolysis at 64 °C, and eventual depolymerization in room-temperature water.

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