Influence of Monoalkoxy Silane on the Dielectric Response of Polypropylene Aluminium Nitride Nanocomposites

Silane coupling agents are widely used in polymer nanocomposites, where they are considered a linker that can increase the compatibility between organic polymers and inorganic fillers. However, the commonly used trialkoxy silanes (TAS) are reported can form a thick layer, which can lead to, e.g. reduction of the AC breakdown strength. In this work, a monoalkoxy silane (MAS) with a single bonding-site to the surface -OH groups of nanoparticles is applied. In this case, the formation of thick multilayers of silane is restricted. Dry samples treated with MAS show a comparable permittivity to the TAS treated counterparts. However, the water absorption behaviour, as well as the complex permittivity tests of wet samples, reveal a major drawback of the MAS treatment: a monolayer or low surface coverage provides an increased real and imaginary permittivity under humid environment.