Monday, December 4, 2023

New, PET-like plastic degrades into sugars in the environment

Plastics are generally tough, corrosion and chemical-resistant, lightweight, and less expensive material, which is great when they’re in use but is not so good when they end up in the environment. At least 14 million tons of plastic end up in the ocean every year, which can harm the environment and biodiversity.

EPFL scientists have now developed a new PET-like plastic material that is easily made from the non-edible parts of plants. The biomass-derived plastic meets the criteria for replacing several current plastics while also being more environmentally friendly. Due to its structure, the new plastic can also be chemically recycled and degraded back to harmless sugars in the environment. It is tough, heat-resistant, and a good barrier to gases like oxygen, making it a promising candidate for food packaging.

“We essentially just ‘cook’ wood or other non-edible plant material, such as agricultural wastes, in inexpensive chemicals to produce the plastic precursor in one step,” says Professor Jeremy Luterbacher at EPFL’s School of Basic Sciences. “By keeping the sugar structure intact within the molecular structure of the plastic, the chemistry is much simpler than current alternatives.”

The new technique is based on the previous discovery of the EPFL team, where adding an aldehyde could stabilize certain fractions of plant material and avoid their destruction during extraction. By repurposing this chemistry, researchers were able to rebuild a new useful bio-based chemical as a plastic precursor.

“By using a different aldehyde – glyoxylic acid instead of formaldehyde – we could simply clip ‘sticky’ groups onto both sides of the sugar molecules, which then allows them to act as plastic building blocks,” says Lorenz Manker, the study‘s first author. “By using this simple technique, we are able to convert up to 25% of the weight of agricultural waste, or 95% of purified sugar, into plastic.”

The resulting bioplastic is suitable for applications ranging from packaging and textiles to medicine and electronics. The plastic can withstand temperatures up to 100-degree Celsius, has a tensile strength of up to 77 MPa, a stiffness of 2,000-2,500 MPa, and forms strong barriers to oxygen and water vapor. The researchers have already made packaging films, fibers that could be spun into clothing or other textiles, and filaments for 3D printing.

“The plastic has very exciting properties, notably for applications like food packaging,” says Luterbacher. “And what makes the plastic unique is the presence of the intact sugar structure. 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.”