Surface Functionalization and Humidity on Charge Transport in PP/TiO₂ and PP/MgO Nanocomposites

This study investigates the influence of polar silane coupling agents (SCAs) on charge transport in polypropylene (PP) nanocomposites containing magnesium oxide (MgO) and titanium dioxide (TiO2) nanoparticles in the presence of water molecules. Surface functionalization results in reduced charge accumulation and electrical conductivity compared with unmodified nanocomposites. Under vacuum-dried conditions, the charge transport is primarily dominated by the types of nanoparticles. It is hypothesized that band bending at the interfaces of MgO used in the PP matrix is more effective in suppressing charges than TiO2. Regarding humidity, the extent of water absorption not only influences charge transport but also contributes to the bonding states between water molecules and nanoparticle surfaces. Despite higher water absorption, band bending at the interfaces in PP/MgO potentially limits the increase in charge transport. In addition, differences in electronegativity during surface functionalization would lead to distinct bonding states with water molecules, resulting in varying energy band levels at interfaces, which in turn influence the ability of materials to capture charge carriers. The most effective charge suppression and reduced electrical conductivity are achieved in ethoxy-modified materials with amino functional groups.