LS Polyamide for High Temperature Applications – Processing and Properties of PA613

The availability of high performance LS materials is still limited to mainly polyamide 11 and polyamide 12 powder. However, these materials do not match to requirements of some advanced applications, for example in the electronics or automotive industry where higher material strengths and temperature resistance is required. The motivation of this project is to robustly process a new material – PA613, delivered by Evonik – and to specify its powder and resulting part properties. Since the material can be processed on regular “low temperature” LS systems like EOS P39x machines, PA613 material promises a great increase of application fields using already industrially established machine types.

Objectives

The new material PA613 is a polyamide especially developed by Evonik for the laser sintering process and therefore not known for conventional manufacturing processes. The advantage of the material in comparison to the standard LS material polyamide 12 is the processing and therefore the assumed application temperature. In this way the application field of laser sintering will be increased. Particularly automotive, electronics and aircraft industries require high temperature polymers where the properties of polyamide 12 are not sufficient. But beside the temperature resistance of the laser sintering systems appropriate polymer powders have to be available. PA613 is a laser sintering powder with high potential for high temperature applications but first of all it has to be processed robustly on a laser sintering machine.

Procedure

The proceeding of the project starts with investigations of the processability of PA613 in general where recoating of the powder is tested and machine parameters are adapted. To reach high quality build parts further parameters, especially laser exposure parameters, are developed in a further procedure. Another topic is the recyclability of used powder. Ageing effects are investigated to get a first hint to the recyclability in general and, if possible, to a suitable refresh strategy. When the material is processable on the LS system and suitable parameters are found, achievable standard part properties of PA613 are tested and an analysis of advanced characteristics demanded by the aimed applications is done.

Latest Results

In the first part of this project the processability of the new laser sintering material PA613 was investigated and suitable process instructions concerning powder recoating, temperature settings and machine modifications were found. A smooth and homogenous powder surface can be generated due to good flowability which was detected by powder characterization. Furthermore, the temperature window, which allows building parts without process failures, is quite high.

In a second step laser exposure parameters were correlated to mechanical properties and it became clear that tensile properties are quite constant for a wide range of laser energy density but can be maximized especially in z-build direction by optimization of contour parameters. The latter might be investigated in a deeper detailed work in the future. For this project, a final laser exposure parameter set could be found which works robustly and was used for further investigations.

Beside build parameters ageing effects of the material were investigated with regard to recyclability of the material. The recyclability of used powder is usually limited due to ageing effects during the manufacturing process. The material is kept at high temperatures for a long time period. To ensure a constant material quality, mixtures of recycled and virgin powder are commonly used for established LS materials. Within this project ageing effects could be found, but which refresh rate is suitable to gain high quality parts is not clarified completely. However, different PA613 part characteristic are determined for virgin powder. PA613 achieves about 25 % better tensile properties than standard LS material PA12 and shows high potential to be implemented in industrial applications.

Outlook

In a follow up project in 2018 the recyclability will be investigated further with the aim to find a suitable refresh strategy and will supplement the material-dependent process instruction already found. Together with defined process parameters further information about achievable part quality especially application relevant characteristics will set the base for an application of the new material in industry. As PA613 is not known in conventional manufacturing, it is important to classify the material within the range of engineering plastics to become a new high performance material in industry. For this purpose, more information about part properties have to be generated in the future.