Characterization of Nanocomposites Based on Silicone Rubber by Ultrashort Pulse Laser Ablation

Nanofillers are added to polymeric insulating materials in order to modify the electrical, mechanical and thermal properties. This study investigates silicone rubber filled with hydrophilic and hydrophobic silica nanoparticles with respect to their resistance to laser ablation and to arc discharges, as well as their mechanical properties. The laser ablation is performed with single femtosecond laser pulses at wavelengths of 520 nm and 1040 nm. This way, the influence of the nanoparticles on the ablation by laser pulses with defined energy is investigated. The energy absorbed in the ablated volume is determined by taking into account the absorption for various fluences above the ablation threshold. For the silica nanocomposites, the energy specific ablation volume (ESAV), i.e., the ablated volume per absorbed energy, is significantly reduced compared to the unfilled polymer. The reduction is more pronounced for hydrophilic nanoparticles than for hydrophobic nanoparticles. Furthermore, the resistance to arc discharges and the mechanical strength of the nanocomposites are higher compared to the unfilled polymer. In particular, for nanocomposites with different types of silica filler particles the resistance to laser ablation, expressed by the ESAV, the resistance to arc discharges and the mechanical strength, expressed by Shore A hardness and the Young's modulus, show a strong correlation. From this, it is concluded that the modifications of the material properties are caused by interactions between the polymer and the nanoparticle surface, i.e., an interphase. The different extent of this interphase becomes obvious in the different degrees of impact on various electrical and mechanical properties.