The role of Hydrophobic and Hydrophilic Functional Groups in Silica Nanoparticles on the Properties of Polypropylene

This study evaluates the hydrophobicity of silica nanoparticles and their role, at varying mass fractions, on the thermal, mechanical, and electrical properties of polypropylene (PP). Nanocomposites with mass fractions of 1.5%, 3%, and 6% were prepared via melt dispersion. Instrumental nanoindentation was employed to determine Young’s modulus and nanohardness. Thermal properties were analyzed using differential scanning calorimetry (DSC) and thermogravimetry (TG), while electrical properties were assessed through Electrochemical Impedance Spectroscopy (EIS). Phase morphology was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Across all samples, regardless of silica fraction and type, no significant changes were observed in the melting behavior of PP. However, higher silica fractions for both types showed increased thermal stability. EIS results indicated a 15% decrease in dielectric conductivity for nanocomposites containing hydrophobic nanoparticles compared to neat PP. Regarding mechanical properties, all nanocomposites exhibited a higher elastic modulus than the matrix, with an increase of up to 67.3% observed in samples containing 3% hydrophilic silica. These findings are interpreted based on the nanoparticle phase’s dispersion state and hydrophobic nature.