This thesis investigates the challenges and opportunities of recycling PA6-GF30, a glass-filled polyamide, to address the pressing environmental concerns surrounding polymer waste. Through a collaboration between Thule Group and Jönköping University, it aims to understand how the properties of recycled materials evolve over time and reprocessing cycles, proposing practical methods for their utilization in sustainable manufacturing practices.

Thule Group's commitment to reducing emissions entails transitioning to sustainable materials, particularly through increased use of recycled engineering materials like PA6-GF30, to lower the carbon footprint of products, emphasizing the importance of maintaining product quality and safety while exploring the effects of recycled materials on mechanical properties.

Through producing and testing post-industrial and post-consumer samples added to virgin PA6-GF30 with varying ratios, comparison with the commercially available polymers was conducted. In total, 15 different mixtures of pellets of different quantity and quality of recycled composites were investigated with tensile test and impact test, moreover the fibers of some batches were filtrated from the matrix and the fiber aspect ratio was examined with the help of an optical microscope.

Results illustrated that recycled polymers generally showed more mechanical property degradation as the ratio of recycled polymers were increased. Furthermore, adding the same amount of post-consumer regrinds as opposed to post-industrial was more detrimental to the overall mechanical performance. Post-industrial composite regrinds performed 11,3% worse in UTS, meanwhile post-consumer regrinds dropped by 25,5% in the same characteristic when the samples made of 100% recycled materials were compared to the virgin composite. 

The reason behind this phenomenon was investigated and supported by microscopy. One of them is the natural aging of the material that operates through chain scission, that slowly makes that polymer stiffer and weaker. The other and more dominant reason is the damage taken by the fibers, that create numerous stress concentration sites at fiber ends, within the structure, ultimately damaging the fiber-matrix interface.