麻豆淫院

Researchers at the University of Bayreuth have found a way to make plastics more sustainable by utilizing sulfur waste from the petroleum refining process. They have developed a method that allows so-called dynamic sulfur bonds to be easily integrated into polyesters. Their findings have been in the journal Angewandte Chemie International Edition.

Polyesters are versatile plastics found in many everyday items such as PET bottles, packaging, rucksacks, and clothing. They are popular due to their potentially easier degradability, making them more sustainable than other types of plastic.

However, even polyesters have room for improvement when it comes to recyclability: during thermal and mechanical recycling processes, quality can deteriorate, meaning that recycled polyester often has inferior properties compared to virgin material. As a result, polyesters cannot be recycled indefinitely.

One promising approach to meeting this challenge involves the incorporation of new chemical bonds that can be easily opened and closed, thus significantly improving the sustainability of these materials.

Dynamic bonds are chemical linkages that can be broken and re-formed with ease, which is crucial for sustainable materials. This allows materials to be repaired or reshaped without being broken down into their basic components. The breaking and re-forming of these bonds is often controlled by a catalyst鈥攁 substance that facilitates or speeds up a chemical reaction.

Elemental sulfur, a by-product of petroleum refining, contains such dynamic bonds. However, integrating dynamic sulfur bonds into polyester has proven difficult. A research team led by Prof. Dr. Alex Plajer, Junior Professor of Macromolecular Chemistry at the University of Bayreuth, has now succeeded in introducing dynamic sulfur bonds into polyesters using a newly developed method.

In addition to elemental sulfur, the method requires epoxides鈥攁 widely used class of chemical starting materials. The researchers discovered that a variety of epoxide types can be used, including those commonly used in industry or even derived from natural sources. This allows the properties of the resulting polymers to be tailored鈥攆or example, whether they are hard or soft, or at what temperature they behave like glass.

In addition, the synthesis of the polyesters only requires a simple catalyst: lithium alkoxide. This compound is easy to produce, user-friendly in lab practice, and enables catalysis under relatively mild conditions, which saves energy and reduces costs.

"Interestingly, we discovered that the involvement of sulfur鈥攑articularly the so-called S8 ring鈥攁ccelerates the reaction introducing the dynamic bond. Certain parts of the resulting polymer appear to support the catalytic process. This is a rather unusual mechanism," says Plajer.

The polyesters produced with dynamic sulfur bonds are stable enough to undergo subsequent modification. Through further chemical reactions, for instance, the material can be crosslinked, enabling its use as a reusable adhesive that can be processed with heat or broken down with acid.