Polyamide 11 nanocomposite feedstocks for powder bed fusion via liquid-liquid phase separation and crystallization

Within this contribution, the incorporation of nanoparticles (SiO2, Al2O3, TiO2) into the matrix of precipitated polyamide particles during thermally induced phase separation (TIPS) is demonstrated. The obtained polymer composite powders are tailored for their application in powder bed fusion (PBF). The flexible process allows to tune and adapt the powder properties to meet specific challenges like narrow particle size distribution, spherical particles, high additive contents and good distribution of the additive within the powder.Thermogravimetric analysis and electron microscopy prove the incorporation of the nano-sized additive into the matrix of the polymer. The influence of the additive material during polymer precipitation on the particle size distribution and shape of the powders is discussed. Thermal properties of the composite powders were assessed by dynamic and isothermal DSC for subsequent Avrami analysis. The observed acceleration of the crystallization kinetics could be attributed to the nucleating effect of the additive.All powders showed an easy-flowing (flow index ffC > 4) behavior. This allowed the deposition of homoge-neous powder layers during PBF experiments also at high temperatures. The processability of the composite powders in the PBF process was demonstrated by single layer experiments.