Aging behavior of polyamide 12: Interrelation between bulk characteristics and part properties

The high process temperatures in combination with long building times during the laser sintering process lead to chemical and physical aging mechanisms on the polymeric feed material. The unmolten partcake material, which acts as a supporting structure, can be removed after each building process and reused for further processes. However, material as well as bulk properties are changed due to thermal and mechanical load during the laser sintering process. Within this paper the interrelation between the aging state, bulk values and resulting part properties like porosity, surface roughness and mechanical behavior are derived. Therefore, polyamide 12 powder is used for at least five processing cycles without refreshing. Before and after each building process, bulk characteristics and changes of the particle surface were determined. Specimens were manufactured during the laser sintering process in order to study the part density, roughness and mechanical behavior.