Technological watch

Scientists from the University of Paderborn, the Hamm-Lippstadt University of Applied Sciences and the Aachen-Maastricht Institute for Biobased Materials (AMIBM) are researching new, environmentally friendly plastic products based on lactic acid.
The aim is to develop sustainable materials for optical applications such as headlights, lenses, reflectors or light guides. These products have so far been made from petroleum-based plastics such as or and thus represent a burden on nature and the environment.
Polylactide to the Rescue
The aim of the scientists is to use a certain family as an optical material in lights and headlights. has proven to be a suitable candidate.
With this approach scientists address several problem areas of conventional polymer materials. The move towards short-term renewable resources helps to establish a materials management system that is independent of crude oil. At the same time, there is a significantly lower CO2 emissions achieved and thus contributed to the goals of the Paris Agreement. A third aspect concerns the consideration of the entire material life cycle.
Avoiding Microplastics while Recycling
The main concern here is the avoidance of microplastics due to . As an exclusively bio-based polymer, polylactide is completely degradable under certain conditions. Long dwell times in nature are therefore excluded. In addition to the properties required for specific applications, these are essential incentives for industry to switch to such alternative materials.
“However, polylactide not only offers advantages in terms of sustainability: It also has very good optical properties for use in the visible range of the electromagnetic spectrum. At the same time, there are large production capacities for polylactide. This makes it relatively competitive in terms of price compared to conventional polymers,” says Prof. Dr. Klaus Huber from the department of chemistry at the University of Paderborn.
Overcoming the Shortcomings with Research
First of all, the use in connection with LEDs, which are known as efficient and environmentally friendly light sources, is being researched. Huber explains: "In particular, the extremely long service life and the emitted radiation at the short-wave end of the visible spectrum, i.e., the high blue component of the LED light, place the highest demands on the optical materials." That is why extremely durable materials must be used. The problem: Polylactide becomes soft at around 60 degrees Celsius. However, LED-based lights can reach temperatures of up to 80 degrees when in operation.
Another challenge is the crystallization behavior. From around 60 degrees, crystallites form, which cloud the material. The scientists are working on either to avoid their formation entirely or to replace the process with controlled crystallization. Only crystallites with dimensions that do not impair the light are formed. “The project should make it possible to use polylactide in sophisticated technical lighting applications for the first time. In concrete terms, the aim is to use it as a lens material in a bicycle headlight.
To this end, scientists work closely with the Busch und Müller company in Meinerzhagen, but other lighting technology companies such as HELLA from Lippstadt are also interested in the progress and see an increasing need for the use of sustainable solutions in their products. “In Lippstadt, we are using specially developed equipment to investigate the resistance of the polylactides developed in the project to short-wave visible radiation,” says Prof. Dr. Jörg Meyer from the Hamm-Lippstadt University of Applied Sciences.
At the Paderborn site, the aim is to determine the molecular nature of the polylactides to be used with a view to the later use of materials. In particular, the melting and crystallization behavior of the developed materials is examined by the scientists. Huber is investigating the extent to which additives or irradiation of the samples improve the behavior about the desired optical properties. "The work is carried out with a small-angle light scattering system specially built for this purpose and allows an investigation of the crystal growth or the melting process of crystals, i.e., precisely the processes that have a significant influence on the optical functionalities," says Huber.
In addition to scientific and technical knowledge, the project is intended to provide significant economic impetus. A sustainable optical bioplastic that has competitive properties improves the competitive situation for lighting manufacturers and automotive suppliers. As part of the project, young scientists will also be trained for industry and research institutions. The team expects the first results at the end of 2022.
Source: University of Paderborn