Monday, May 23, 2022

New degradable plastic breaks down in sunlight and air within a week

Plastic pollution is one of the threats with the greatest impact and is now starting to become a huge problem. Plastic waste chokes shorelines and oceans, in part because plastic polymers do not easily decompose. This would not be the case if every plastic, like the new one, would break down in about a week in sunlight and air.

The novel degradable plastic material has been developed by researchers from China’s Huazhong University of Science and Technology, and it came into existence while working on an advanced type of chemical sensor. The researchers were developing a polymer film that changes color depending on pH levels. But then they noticed that the plastic’s natural deep red color faded quickly, and the plastic film broke apart over several days in sunlight.

“In conjugated polymers such as this, which have a long backbone chain of alternating double and single bonds, the material’s color comes from its molecular structure – long chains of monomers – rather than a dye. Loss of that color means the chains have broken down into their monomer units,” explain researchers.

Breaking these bonds is a common goal of research into better recycling of plastics, which means that the scientist accidentally created a promising, environmentally degradable version of this material.

New degradable plastic breaks down in sunlight and air within a week
The red plastic film breaks apart in sunlight and air over 7 days. Here, each vial represents a day from 0 to 7, left to right. Credit: Qiang Yue

Techniques such as chemical characterization using nuclear magnetic resonance (NMR) and mass spectroscopy showed that this plastic decomposes rapidly in sunlight from a petroleum-based polymer into succinic acid, a naturally occurring non-toxic small molecule that doesn’t leave microplastic fragments in the environment.

A sun-sensitive plastic might not be a good choice for bottles or bags that need to last more than a week on the shelves. However, integrating the environmentally degradable polymer as a minor ingredient or with other biodegradable polymers could help speed the breakdown of these materials in landfills.

Another possible application of this degradable plastic would be in the field of electronics. When sealed inside a cell phone and other flexible electronic devices, the polymer could last for years without contact with light and oxygen that trigger decomposition. In this way, disposing of devices at the end of their service life would be easier. Its by-product, succinic acid, could be upcycled for commercial uses in the pharmaceutical and food industries.

We will continue to explore the degradation of plastics,” says coauthor Liang Luo, looking ahead. Though he doesn’t have a timeline for commercialization, he says the ballpark “could be 5 or 10 years.”


New Discoveries