Abstract
This study investigated the effects of multiple laser sintering (LS) cycles on a polyamide 12 powder mixture of 70% recycled material and 30% virgin polymer. This research aimed to understand how repeated LS processing influences this specific powder mixture's thermal and structural properties, which is crucial for optimising its performance in additive manufacturing applications. A thermal analysis revealed significant changes in the thermal behaviour of the powder over successive build cycles. Specifically, there was an observed increase in both the melting temperature and the crystallinity of the powder, alongside a notable decrease in the crystallisation temperature. These alterations suggest that the repeated LS cycles affect the thermal profiles and potentially enhance the material's stability and usability in additive manufacturing processes. Additionally, a particle size distribution analysis indicated statistically significant differences between the initial and post-sintering states of the powder. These differences are significant as they can influence factors such as flowability and packing density, which are critical for the efficiency of additive manufacturing applications. Microscopic observations further revealed a strong correlation between the crystal morphologies and particle shapes, indicating that the structural changes occurring during processing are inter-related. The relationship underscores the importance of understanding microstructural evolution and the mechanical properties of the final printed products. These findings provide crucial insights into the microstructural evolution and thermal behaviour of recycled PA12 powder during multiple LS processing cycles. This study aids in developing practical strategies for sustainable and efficient powder recycling within the realm of additive manufacturing. By examining the intricate dynamics at play, the research opens avenues for enhancing the performance and environmental sustainability of 3D printing technologies, making them more accessible for various industrial applications.