Polypropylene Filled With Glass Spheres in Extrusion‐Based Additive Manufacturing: Effect of Filler Size and Printing Chamber Temperature

Abstract

A challenge in extrusion‐based additive manufacturing of polypropylene (PP) filled with spherical particles is the combination of decent processability, excellent warpage control, and the retention of the tensile strength of neat PP. This study addresses this issue by adopting two approaches. Firstly, different size fractions of borosilicate glass spheres incorporated into PP are compared. Secondly, the temperature of the printing chamber (TCh) is varied. The effects of these features on the thermal, crystalline, morphological, tensile, impact, and warpage properties of 3D‐printed parts are examined. Smaller glass spheres (<12 µm) are found to be superior to larger fractions in all investigated aspects. Notably, the corresponding composites show higher tensile strengths than neat PP. An increase in TCh results in a more homogeneous temperature distribution within the printing chamber and promotes annealing during printing. Consequently, the dimensional accuracy of printed parts is improved. Additionally, β‐crystals and larger spherulites are formed at a higher TCh.

Polypropylene Copolymers Designed for Fused Filament Fabrication 3D‐Printing

“…Printing parameters could have been optimized further with more material available. More material is also beneficial for filament production, since it can be done by an extruder; stabilizers and fillers can be added simultaneously keeping degradation at an acceptable level and improving shrinkage 14,15. In a follow‐up step, the materials should be fully characterized concerning material testing: tensile tests, etc., which necessitates the upscaling of the polymerization.…”

Filament Materials Screening for FDM 3D Printing by Means of Injection‐Molded Short Rods

“…For the development of FDM feedstock materials, the neat polymers were compounded and processed using standard single‐screw filament extrusion lines . The use of such lines requires considerable time and at least 1 kg material for an extrusion process optimization to achieve satisfying filament quality for further FDM printing.…”

“…M. Spoerk et al. used a PP copolymer for filament extrusion and added different types of fillers . In these studies, they investigated the dimensional stability and volumetric shrinkage of printed parts bonded to the build surface.…”

“…[19,20] For the development of FDM feedstock materials, the neat polymers were compounded and processed using standard single-screw filament extrusion lines. [21][22][23][24][25][26][27][28][29] The use of such lines requires considerable time and at least 1 kg material for an extrusion process optimization to achieve satisfying filament quality for further FDM printing. For instance, Carneiro et al used a glass fiber reinforced standard injection molding grade of isotactic PP (iPP) as a filament for FDM.…”

“…[30] M. Spoerk et al used a PP copolymer for filament extrusion and added different types of fillers. [25,[27][28][29] In these studies, they investigated the dimensional stability and volumetric shrinkage of printed parts bonded to the build surface. However, the mechanical properties of investigated materials were determined directly on filaments and no interlayer bonding studies were included.…”