Semi-Crystalline Polyetherimide Microparticles via Liquid-Liquid Phase Separation and Precipitation

A novel approach for production of polyetherimide (PEI) microparticles by liquid-liquid phase separation (LLPS) and precipitation is demonstrated and the effect of the used solvents acetophenone and dimethyl phthalate on the obtained powders is outlined. Interestingly, the method allows one to produce semi-crystalline particles, while PEI is known to be hard to crystallize and typically obtained in amorphous form. To get a deeper understanding of the phase behavior of the polymer-solvent systems, cloud point curves in dependence on system composition are determined. The obtained particles are thoroughly characterized. They are highly semi-crystalline, as proven by DSC and X-ray diffraction and are an ideal novel feedstock for powder bed fusion of polymers with laser beam (PBF-LB/P). Polymorphism and, thus, thermal characteristics like the melting point, can be tuned by the used solvent. After heating the precipitated powder samples above their melting temperature and subsequent cooling fully amorphous polymer is obtained, which is assessed to be advantageous with respect to mechanical properties (toughness) of the PBF-LB/P-produced component from this novel feedstock.