Researchers discover why plastic sheds dangerous fragments

In a new study, scientists have delineated the molecular process that causes these small pieces to break off in such large quantities. Since hitting the market 75 years ago, plastic has become ubiquitous -- and so, presumably, have nanoplastics. As it turns out, the qualities that make plastic strong and flexible also make it prone to forming nanoplastics -- this is true for 75-80% of all plastics used, which are termed as semicrystalline polymers in the community. Sanat Kumar, Michael Bykhovsky and Charo Gonzalez-Bykhovsky Professor of Chemical Engineering at Columbia Engineering, led the research effort.

If you look at a piece of plastic through a powerful microscope, you'll see alternating layers of hard material and soft material. In the hard layers, plastic molecules are rigidly organized in strong crystal structures. In the soft layers, the molecules lack structure and form a soft, amorphous mass. When thousands of these layers are stacked together, they create a material that's lightweight, durable, and extremely versatile. Importantly these materials derive their unique properties through the connectivity between the soft and hard phases.

In a paper published March 28 in Nature Communications, the researchers explain how nanoplastics form. They discovered that the process begins in the soft layers, which grow weaker over time due to environmental degradation and can break off even when the plastic is not under stress. By themselves, these soft pieces break down quickly in the environment. Problems arise when the failure of a soft layer allows hard layers to break off. These crystalline fragments are the nano- and microplastics that can persist in the environment for centuries and cause significant damage in living things, including humans.