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

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 (T-Ch) 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 mu m) 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 T-Ch 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, -crystals and larger spherulites are formed at a higher T-Ch.