Polypropylene/SiO2 nanocomposites with improved mechanical properties

Polypropylene-SiO2 nanocomposites were synthesized using twin-screw extruders. The properties of the nanocomposites were studied using two different inorganic fillers: colloidal (sol) and powder silica nanoparticles. Reinforcing and toughening effects of the nanoparticles on the polymer matrix were found at a loading of 4.5 wt.%, which is lower than for most particulate filled composites. The use of silica nanoparticles led to different microstructure when compared with that of the pure polymer. Addition of colloidal silica to the polymer matrix produced good filler dispersion while the use of powder silica resulted in aggregated silica particles in the polymer matrix. There was no noticeable improvement of the mechanical properties when powder silica was added to the pure polymer. On the contrary, the presence of silica-sol nano-particles in the polymer matrix led to an increase of both Young modulus and impact strength, from 1.2 GPa to 1.6 Gpa and from 3.4 kJ/m2 to 5.7 kJ/m2 respectively.