Circular-ready and biobased materials for the sports industry

In product development as it is practiced today, the material of each individual component is selected based on its individual suitability for the task in the product. As a result, the composition of sports equipment follows a multi-material design.
For example, bicycle helmets today consist of an EPS core that absorbs the shock, a possibly fiber-reinforced polycarbonate shell (PC) that stiffens and protects against mechanical impacts, injection-molded parts made of polyethylene terephthalate (PET), such as the clips of the belt and the sun visor, and belts made of nylon fabric (polyamide, PA). To separate these components from each other would require a lot of manual labor, which would reach its limit at the latest when separating the shell and core. As a result, multi-material systems like helmets are directly subjected to thermal recycling. The demand for recyclable and sustainable products within the sporty industry is also steadily increasing. Thermoplastic self-reinforced plastics (srP) offer a promising alternative to conventional fiber-reinforced materials. By using the same base polymer as the fiber and matrix material, material recycling back into the same application is made possible. The self-reinforcement of these materials is based on the drawing of the fibers and the resulting high degree of orientation of the polymer molecules. These innovative materials combine the advantages of highly abrasion-resistant fibers, as well as a high energy absorption with an improved recyclability. Partial consolidation, as shown in Figure 1, allows for direct integration of stiffening ribs into the fabric. By further combining with foams, compact material and fleeces, all based on the same polymer, a modular system of material morphologies is created, as shown in figure Figure 4. Considering the respective requirements, these morphologies can now be combined to design different sports equipment. A possible application is achieved by using a sandwich approach, as shown in Figure 2. For this, the cover layers are joined adhesive-free with a foam based on the same polymer.
The presented materials and processes offer a high degree of flexibility in terms of reinforcement, installation space, load introduction, haptics and other properties of the components. Already now, complex components can be manufactured using the process technology developed at the Fraunhofer ICT on conventional processing plants, as shown by a PLA-based bicycle helmet in Figure 3. This opens new possibilities for the industrial production and application of these materials. In the sports and leisure industry, these materials can be used for helmets, textiles, backpacks and protectors, among other things. They are also suitable for use in semi-structural applications. The overall goal of the materials presented in this lecture and their potential applications in the sports industry is to realize resource-saving and lightweight equipment for various sports through a complete recycling of the materials. This requires a rethink in material selection and processing, as well as the implementation of new recycling processes. The development and application of thermoplastic self-reinforced plastics represent a significant step towards a more sustainable and resource-efficient future of the sports industry.