Characterization of thermally treated polypropylene powders with wide sintering window for powder bed fusion of polymers

One key issue restricting semi-crystalline polymers to be widely applied in powder bed fusion (PBF) of polymers is lack of good powder processability, especially a wide sintering window. In this work, a thermal treatment method with mixed dispersant system (TTMS) was developed to modify a common isotactic polypropylene (PP) powder to adapt for PBF. Both sintering window (SW) and particle morphology of the PP powder were improved by the TTMS process. The SW was expanded from 15 degrees C for the raw PP powder to 51 degrees C for the TTMS-PP powder, since the TTMS process facilitated the formation of a crystal with larger lamellar thickness as revealed by differential scanning calorimeter and X-ray diffraction measurements. Moreover, the particle size of the TTMS-PP powder was reduced to 60 mu m, which was only a third of the raw PP's size. Consequently, the TTMS-PP powder exhibited a lower flow energy compared to the raw PP powder. These improvements contributed to a better laser processability of the TTMS-PP powder, as demonstrated by the single-layer component with reduced part deformation and better dimensional accuracy. This work is believed to provide a useful guideline for the development of semi-crystalline polymer powders for the PBF technology.