An improvement in the mechanical properties of polypropylene/ethylene-propylene-diene monomer/titanium dioxide nanocomposite obtained by fused filament fabrication

In the present research, the PP/EPDM/TiO₂ nanocomposite was fabricated using the fused filament fabrication process to improve the mechanical properties of the obtained samples. For this purpose, first the response surface methodology was used to investigate the effect of TiO₂ content, nozzle temperature and printing speed on the responses of tensile strength and elongation. Then, the desirability function method was applied to find the optimal condition of the process parameters. The fracture surface of the tensile samples was also studied by scanning electron microscopy, differential scanning calorimetry and thermogravimetric analysis to find a relationship between the microstructure and mechanical properties of the fabricated samples. The results indicated that the highest elongation of samples (144.9%) was attained at a TiO₂ content of 4 wt%, while the tensile strength of samples was maximized (24.6 MPa) at a TiO₂ content of 2 wt% due to fine dispersion of the nanoparticles. An increase in the nozzle temperature from 200 to 225°C led to an enhancement in the tensile strength (11.2%) and elongation (15.7%) of samples because of the good viscosity of the filament, whereas the tensile strength (6.6%) and elongation (11.1%) of samples were decreased with the increase of nozzle temperature from 225 to 250°C because of the thermal degradation of filament. Moreover, when the printing speed raised from 20 to 40 mm/s, the tensile strength initially improved by 2.7% and then decreased by 1.2%, but the elongation continuously decreased by 6.3%. Nevertheless, the concurrent enhancement of the tensile strength and elongation has been obtained at a TiO₂ content of 2.5 wt%, nozzle temperature of 227°C and printing speed of 28 mm/s.