From medical functions to sporting items: Biocompatible and sustainable plastics


Medical tubing is one of a number of applications for polyurethanes. Fraunhofer researchers have now produced this plastic without toxic isocyanates, while at the same time using carbon dioxide sustainably. Image: Fraunhofer IAP

Many plastic products are made from polyurethanes. Fraunhofer researchers have developed a manufacturing process for polyurethanes that avoids the use of toxic isocyanates and at the same time uses carbon dioxide as the starting material. In cooperation with partners from industry, polyurethanes are developed with a reproducible standard. The research results can be seen from November 15 to 18 at MEDICA 2021 in Düsseldorf (Hall 3, Stand E74).

Polyurethane is a multipurpose material. This type of plastic is used as foam for mattresses, as packaging material, as elastic material for sporting goods and as sealing material, paint, glue, construction foam and much more. The material is even used in medical applications – for example in the form of tubes for intravenous catheters. Researchers at the Fraunhofer Institutes for Applied Polymer Research IAP, for Chemical Technology ICT, for Manufacturing Technology and Applied Materials Research IFAM and for Environmental, Safety and Energy Technology UMSICHT are now breaking new ground to produce this plastic sustainably and without the use of toxic materials.

Non-toxic: no isocyanates

A modular system made up of three building blocks is generally used to manufacture polyurethanes: isocyanates, chain extenders and polyols. The product properties can be controlled very precisely using the recipe and process parameters. Due to the high reactivity of the isocyanates, the products can be manufactured in a few minutes. But there is a downside. Isocyanates are toxic and sensitizing substances that can cause allergic reactions and asthmatic symptoms. The European Chemicals Agency EChA has therefore decided on a restriction: From 2023, only specially trained staff will be allowed to work with formulations that contain more than 0.1 percent isocyanate.

“With our new synthesis we avoid toxic isocyanates and thus enable safer production processes. The polyurethane produced in this way can also be certified as biocompatible, ”explains Dr. Christoph Herfurth, scientist at the Fraunhofer Institute for Applied Polymer Research IAP and coordinator of the project. To do this, the researchers replaced the isocyanates with dicarbamate. They aim to make the process efficient and industrially feasible. The research teams are now also working on more sustainable means of foaming the polyurethanes.

Sustainable: the use of carbon dioxide

“Instead of using fossil fuels such as crude oil or natural gas as the carbon source for the polyurethanes, we use carbon dioxide and polyurethane recyclates,” explains Herfurth. “In this way we can recycle the carbon and ensure that less harmful CO2 is released into the atmosphere.” This process is already underway; This requires pressure and elevated temperatures. The researchers at the Fraunhofer Institutes are currently working on optimizing the processes.

Innovative: various demonstrators

Initially, the project team will concentrate on developing the building blocks for polyurethane production. The researchers are also investigating the relationships between the process parameters and the structural properties: How do you achieve the properties that make conventional polyurethanes so versatile? Three different demonstrators illustrate the various applications of this new form of polyurethane: Firstly, sustainable tubes for medical applications. Only comparatively small amounts of polyurethanes are required here. This makes it easier to introduce a new product. In a second application at Fraunhofer IFAM, optimized adhesives are being developed for the new polyurethanes in order to connect cannulas with medical tubes, for example for catheters. The third demonstrator on the agenda is foam and thus processing technologies for mass products.

New process gives polyurethane waste a second life Provided by the Fraunhofer-Gesellschaft

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