Polypropylene (PP) parts produced by extrusion-based
additive manufacturing (EB-AM) suffer from warpage
issues due to their high degree of crystallinity and ori-
entations introduced during printing. These issues can
be overcome by the addition of spherical fillers. How-
ever, the low aspect ratio of the filler and high filling
degrees necessary for preventing warpage downgrade
the mechanical properties, especially the toughness.
This study aims at optimizing a PP-compound contain-
ing spherical glass microspheres for the application in
EB-AM by maximizing the matrix–filler compatibility
and therefore the printability, tensile properties and
toughness, while still counteracting dimensional inac-
curacies. A detailed study on the tensile, fracture, ther-
mal, rheological, and impact properties of various
compounds containing different glass types was con-
ducted. It was shown that for EB-AM applications, PP
compounds based on borosilicate glass spheres out-
perform compounds filled with the conventionally used
inorganic soda lime glass. The proposed optimized
composite exhibits an exceptional interfacial adhesion
between the microspheres and the matrix and a homo-
geneous filler distribution. It offers an improved pro-
cessability and tensile properties up to the yield point
comparable to those of neat PP. In a concluding
impact test on printed composites, the optimized sys-
tem exhibited impact energies 80% higher than com-
pounds containing the conventionally used glass.