Comparison of Micro/Nanosized <scp> SiO ₂ </scp> Reinforcement Impact on Mechanical, Thermal, and Hydrophobicity of Polypropylene Composite Compatibilized With Polypropylene‐Graft‐Maleic Anhydride Copolymer ( <scp>PP</scp> / <scp>PP</scp>

ABSTRACT This study investigates the effect of the particle size of silicon dioxide (SiO 2 ), specifically micro‐size (m‐SiO 2 ) and nano‐size (n‐SiO 2 ), on the properties of polypropylene (PP)/polypropylene‐grafted maleic anhydride (PP‐g‐MA) composites. The composites were prepared by melt mixing in a twin‐screw extruder, followed by compression molding. Based on mechanical and thermal characterization, the inclusion of m‐SiO 2 enhanced composite rigidity but reduced ductility and flexibility, whereas n‐SiO 2 exhibited the highest maximum decomposition temperature (T peak ), indicating high thermal stability. FTIR analysis confirmed the formation of hydrogen‐bonding interactions between SiO 2 and PP‐g‐MA, thereby enhancing filler‐matrix adhesion. Furthermore, XRD results demonstrated that particle size plays a crucial role in governing the interfacial behavior of the composites. Morphological and surface properties indicate that the incorporation of n‐SiO 2 into the matrix PP/PP‐g‐MA results in a more homogeneous dispersion with lower levels of agglomeration and pull‐out defects compared to m‐SiO 2 , leading to a denser and more cohesive composite structure. This improved morphology promotes stronger interfacial interactions and significantly enhances the hydrophobic surface properties of the composites, as evidenced by a 9.91% increase in the water contact angle for the n‐SiO 2 based composite compared with the m‐SiO 2 filled composite.