Aging effects of polyamide 12 in selective laser sintering: Molecular weight distribution and thermal properties

The material aging in selective laser sintering SLS of polyamide 12 is one challenge, which has to be overcome for implementation of this technique in serial production. High temperatures and along going processing times lead to chemical and physical aging effects of the supporting partcake material. Resulting aging mechanisms are not understood up to now. The investigations in this study aims at the influence of processing time and temperature on molecular changes and thermal properties of polyamide 12 partcake material in selective laser sintering. The focus of the investigations lays on the global heat exposure of the of the bulk material und thus on global material changes. Gel permeation chromatography analysis was used to determine the molecular weight distribution and changes of polymer structure. The Mark-Houwink plot exhibits a linear chain growth, which is a hint for a resulting solid state polycondensation. With increasing build time and build chamber temperature the average molecular weight is rising, whereby the influence of build time is more significant. The rise of chain length leads to a reduction of crystallization temperature, which was detected by DSC.