Even though glass is praised for being fully recyclable, the US Environmental Protection Agency states that only about a third of discarded glass items actually get recycled. With that problem in mind, scientists have developed a new type of glass which is biodegradable.
Created by researchers at the Chinese Academy of Sciences, the experimental glass is made from either of two chemically modified ingredients – amino acids or peptides. Amino acids are molecules which combine to form proteins, while peptides are short chains of amino acids.
The production process begins by heating amino acid or peptide powder in an inert gas atmosphere, past its melting point but not all the way up to its molecular decomposition temperature.
That molten material is then subjected to a supercooling treatment, allowing it to be cooled below what would ordinarily be its freezing temperature, without freezing solid. Finally the material gets quenched with water, causing it to rapidly transform into a clear solid state without crystalizing.
In lab tests, the glass was found to exhibit "excellent optical characteristics, good mechanical properties and flexible processability," the latter referring to the fact that it could easily be cast into commercial molds or 3D-printed. And importantly, when pieces of the glass were composted, microbes in the soil broke them down within three weeks to 7.5 months, depending on the specific amino acids or peptides used.
Mouse studies also showed that the glass harmlessly biodegrades within the body, suggesting that it could be utilized in applications such as drug-dispensing implants which don't have to be removed after their job is done.
"The concept of biomolecular glass, beyond the commercially-used glasses or plastics, may underlie a green-life technology for a sustainable future," said the lead scientist, Prof. Yan Xuehai. "However, the biomolecular glass is currently in the laboratory stage, and far from large-scale commercialization."
A paper on the research was recently published in the journal Science Advances.
Source: Chinese Academy of Sciences
