Composite filaments of ABS/expanded perlite microspheres for fused deposition modelling (FDM) applications: the effect of filler size and density

The study investigated the potential use of expanded perlite microspheres as fillers in ABS composite filaments for 3d printing application, with a focus on the effect of the filler size and density on the major properties of the filament and printed objects. A Vertical Electrical Furnace (VEF) prototype was employed for the preparation of filler grades of varying bulk densities (250, 375 and 500 kg/m³) and size distributions (D90 of 200 to 250 μm), which were used for the preparation of composite filaments, incorporating them in the ABS matrix under constant volume fraction of 20% using a screw extruder. The characterization campaigns focused on the physical and mechanical properties of the filaments, and on the microstructure, mechanical properties, rheology and printing quality of the printed objects. Results from the characterization campaigns revealed that the addition of microspheres’ filler improved shrinkage and warpage deformation of ABS polymer, with a parallel reduction of ductility and melt flow index. However, these changes, did not affect the melt extrusion process during printing. Particles survival rate increases by increasing the bulk density and decreasing size, with bulk density of 350 kg/m³ or higher being beneficial due to the higher strength. Overall, expanded perlite microspheres present adequate performance as a filler in ABS for 3D printing applications, provided the appropriate grade is used, while as inorganic, non-toxic and natural material can improve the environmental footprint of ABS and potentially of other conventional thermoplastics used for the filament preparation.