Rheological, Viscoelastic, and Dynamic Mechanical Behavior of ZnO-Filled and MA-Modified PP/SEBS Filaments for Fused Filament Fabrication

Immiscible polyolefin–elastomer blends often exhibit limited impact resistance and unstable melt-flow behavior due to weak interfacial adhesion and inefficient stress transfer between phases. These limitations are relevant for fused filament fabrication (FFF), where filaments must withstand feeding, extrusion, deposition, and service loading. In this work, PP/SEBS (70/30 wt %) blends modified with maleic anhydride (MA) and ZnO nanoparticles were investigated to determine the influence of interphase engineering on the rheological, viscoelastic, dynamic mechanical, and FFF performance of PP/SEBS filaments. Four formulations (PP/SEBS, PP/SEBS-1%ZnO, PP/SEBS-3%MA, and PP/SEBS-1%ZnO-3%MA) were produced as 1.75 mm filaments and characterized by rotational rheology, DMA, tensile and notched Izod impact tests, SEM, and FTIR. All systems exhibited shear-thinning behavior, while the PP/SEBS-1%ZnO-3%MA formulation showed the most balanced melt response, combining reduced viscosity with adequate viscoelasticity. SEM and DMA analyses suggested improved interphase stability and more efficient viscoelastic dissipation in MA-containing systems. The PP/SEBS-1%ZnO-3%MA blend achieved the highest impact strength (46.86 ± 0.73 kJ m–2), approximately 60% higher than PP/SEBS, while maintaining tensile performance. Preliminary FFF trials demonstrated stable deposition and good dimensional reproducibility. These results demonstrate that MA/ZnO interphase engineering is an effective strategy for improving rheological stability and impact reliability in PP/SEBS filaments for FFF applications.