(38f) Extrusion 3D printing of impact modified nylon 6 blends:  A study on the effect of printing parameters on performance

The worldwide demand for additive manufacturing (AM) is increasing exponentially due to its ability to fabricate products of complex shape, along with its cost-effectiveness, reduced time, higher efficacy, higher precision and freedom of material utilization. In the current research work, fused deposition modeling (FDM)-based 3D printing of nylon 6 was performed and issues such as warping, filament clogging, and layer delamination were targeted to improve its poor printability. Nylon 6 was modified through incorporating of an impact modifier and chain extender. The analytical properties, such as rheology, thermal and melt flow index (MFI), of the modified nylon 6 were performed to observe its suitability for 3D printing. Melt rheology showed an improvement in the storage and loss modulus, as well as the complex viscosity of modified nylon 6 due to the formation of complex molecular structure network via branching. Due to being a semi-crystalline polymer, nylon 6 showed various issues, such as wrapping, nozzle clogging, material flowability and layer delamination. Such problems were fixed by adjusting various 3D printing parameters, including printing temperature, print speed, bed temperature and the cooling speed of modified nylon 6. At optimized 3D printing conditions, the impact strength (~543 J/m) of modified nylon 6 was observed to be significantly higher as compared to injection moulded pristine nylon 6. The 3D printed modified nylon 6 showed a heat deflection temperature (HDT) of ~82.5 °C, which is a vital property for 3D printed prosthetics. A higher coefficient of linear thermal expansion (CLTE) was observed in the normal direction as compared to the flow direction, due to the polymer crystal orientation in one direction during processing. Scanning electron microscopy (SEM) images confirmed the formation of voids during printing, which were found to be culpable for density reduction. The void structure can be adjusted through varying the distance between the nozzle and printing bed.

Acknowledgments
The authors would like to thank the following for their financial support: the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) – University of Guelph- Bioeconomy Industrial Uses Program Theme (Project # 030485); the Ontario Ministry of Economic Development, Job Creation and Trade ORF-RE09-078 (Project #053970 and 054345) and Natural Sciences and Engineering Research Council (NSERC), Canada Discovery Grants (Project # 400320).