Mechanical recycling of PET and PA blended textiles with elastane: Process optimization in pretreatment by improving pellet quality with variable binding agents on a laboratory scale

The mechanical recycling of thermoplastic textile waste is facing increasing challenges due to growing waste volumes and stricter regulatory requirements. Particularly problematic are blended textiles such as polyester (PET) or polyamide (PA) mixed with elastane, which are difficult and labor-intensive to recycle using conventional methods. The long-term goal is to process these materials into high-quality and ecologically sustainable recyclates through mechanical recycling, enabling the efficient handling of high input volumes with relatively low logistical effort. To achieve this, pretreatment plays a crucial role, as it significantly influences both processing performance and final material quality through recycling-related optimization of input streams. The elastomeric component, in particular, negatively affects process stability and recyclate quality, thus requiring tailored pretreatment and recycling strategies. This study presents a lab-scale recycling approach focusing on pretreatment, specifically pelletizing after shredding. The aim is to densify and homogenize the fluffy flakes to improve flowability and dosing consistency in downstream processes like extrusion. Precise pelletizing control is key to achieving uniform pellets and stable recycling of complex, mixed-fiber textile blends that are currently difficult to recycle. Various mixing ratios of PET (100 %, 88 %) and PA (100 %, 94 %, 85 %, 80 %) with elastane were examined, with a focus on the influence of different added binders and shredding sizes (12 mm, 8 mm) on pellet structure. The resulting pellets were analysed in terms of their shape, bulk density, dust content and thermal processing behaviour with regard to mechanical recycling. Initial results show that reproducible and dimensionally stable pellets can also be produced from elastane-containing textiles by specifically adapting the pelletizing process parameters such as temperature, sieve sizes and binders. These results provide a good basis for the further development and upscaling of mechanical recycling processes for textile fractions and are also the prerequisite for efficient downstream extrusion and injection molding applications.