Role of processing procedures and molecular weight and their link to quasistatic and fatigue properties of polyamide 6

To expand the scientific base for the usage of the fused layer modelling (FLM) process for the production of polyamide 6 (PA 6) parts, in this work the influence of processing (injection moulding, compression moulding and FLM) and molecular weight on the end-use properties of PA 6 is elucidated. Besides its viscosity, the molecular weight of PA 6 also influences crystallinity and crystallization temperature. The mechanical properties of the fabricated specimens were studied in detail, also in the fatigue range, and analysed focusing on the fusion of interfaces in compression moulding and fused layer modelling. The analysis reveals, that the molecular mobility in the melt (i.e. viscosity and diffusion coefficient) as well as the amount and orientation of interfaces (as determined by the processing procedure) strongly influences the end-use properties. In the case of FLM printed parts, mechanical failure due to quasistatic and fatigue loading essentially depends on the quality of fusion of adjacent layers, which is strongly determined by molecular weight and processing temperature. Generally, a lower viscosity of PA 6 favours fusion of adjacent layers.