Polypropylene with clay–filled for fused filament fabrication: comparative study of the mechanical performance of injected and 3d printed composite

Fused filament fabrication (FFF) is one of the most used 3D printing techniques; however, the lack of printable materials is its main limitation. Polypropylene (PP) is a promising thermoplastic polymer that offers cost and chemical stability advantages over PLA, but its dimensional instability often leads to poor mechanical performance of printed parts. In this study, a PP filament for FFF was developed, incorporating copper ion-saturated clay (Cu 2+ ) and copper oxide nanoparticles (CuO NPs), and the effect of various clay percentages on the tensile properties of the polymer matrix was investigated. The goal was to evaluate the potential use of polypropylene/clay composites as raw materials for FFF. The PP with clay did not form intercalation or exfoliation systems due to the poor matrix-filler interaction, behaving as a microcomposite. Chemical and bactericidal properties were not significantly affected compared to pure PP after the incorporation of clay. However, the thermal stability improved, and the β phase was induced in the crystallization process, enhancing layer adhesion, and reducing deformation during the PP printing process. All injected composites exhibited improved tensile properties, while the opposite effect was observed for printed composites. The best formulation was found for the composite with a 3.0% weight loading of MMT-type II, which showed a 14% increase in tensile modulus for the injected piece and a 17.6% decrease for the printed piece. Despite the reduced mechanical performance in printed pieces compared to injected ones, the material demonstrated processability and printability due to the reduced deformation, which the polymer matrix alone under industrial conditions does not permit.