Thermal, electrical, and mechanical properties of addition‐type liquid silicone rubber co‐filled with Al₂O₃ particles and BN sheets

Abstract

The addition‐type liquid silicone rubber (ALSR) co‐filled with spheroidal Al2O3 and flaky BN was prepared by the mechanical blending and hot press methods to enhance the thermal, electrical, and mechanical properties for industrial applications. Morphologies of ALSR composites were observed by scanning electron microscopy (SEM). It was found that the interaction and dispersion state of fillers in the ALSR matrix were improved by the introduction of BN sheets. Thermal, electrical, and mechanical performances of the ALSR composites were also investigated in this work. The result indicated that the thermal conductivity of ALSR can reach 0.64 W m−1 K−1 at the loading of 20 wt% Al2O3/20 wt% BN, which is 3.76 times higher than that of pure ALSR. The addition of Al2O3 particles and BN sheets also improve the thermal stability of ALSR composites. Moreover, pure ALSR and ALSR composites showed relatively lower dielectric permittivity (1.9–3.1) and dielectric loss factor (<0.001) at the frequency of 103 Hz. The insulation properties including volume resistivity and breakdown strength were improved by the introduction of flaky BN in the ALSR matrix. The volume resistivity and characteristic breakdown strength E0 are 6.68 × 1015 Ω m and 93 kV/mm, respectively, at the loading of 20 wt% Al2O3/20 wt% BN. In addition, the mechanical characteristics including elongation at break and tensile strength of ALSR composites were also enhanced by co‐filled fillers. The combination of these improved performances makes the co‐filled ALSR composites attractive in the field of electrical and electronic applications.

Review of the Performance of High-Voltage Composite Insulators

“…By decreasing the filler size from micro to nano, the thermal conductivity increases with the increase in filler content [ 53 ]. Similarly, a filler with a high aspect ratio (i.e., ratio of the maximum to the minimum dimensions of the filler) also helps to form a composite of high thermal conductivity [ 52 ]. These observations lead us to conclude that by increasing the filler volume with filler particles of a larger size, thermal conductivity decreases due to increased porosity [ 39 ].…”

“…Furthermore, the pores/voids inside the bulk polymeric insulator may cause initiation of partial discharge activities and decrease the dielectric strength due to the accumulation of charge [ 52 ]. The occurrence of electrical discharges on the surface is the root cause of the surface degradation of a polymeric insulator, which ultimately leads to complete failure.…”

“…The higher tensile strength of silicone rubber composite filled with SiO 2 was attributed to the stronger interfacial interaction between SiO 2 particles and silicone rubber as compared to ATH particles and silicone rubber. On the other hand, the irregular shape of a filler having a high particle aspect ratio limits the contents of filler (to avoid sedimentation), and thus the tensile strength may not increase much [ 52 ]. For example, it has been reported that the tensile strength of BN-filled SiR is lower as compared to its ATH-filled counterpart.…”

Binary Promoter Improving the Moderate-Temperature Adhesion of Addition-Cured Liquid Silicone Rubber for Thermally Conductive Potting

“…The poor mechanical properties of pure LSR limit its practical applications [ 9 ]. Researchers have expended great efforts to incorporate reinforcement fillers and functional fillers into LSR to improve its mechanical properties and introduce additional properties such as thermal conductivity and electrical conductivity [ 10 , 11 , 12 , 13 ]. LSR can be imparted with suitable thermal conductivity for efficient heat dissipation by doping with high thermal conductivity fillers such as carbon-based fillers, boron nitride, aluminum nitride, aluminum oxide (Al 2 O 3 ) and so on [ 12 , 13 , 14 , 15 , 16 ].…”

Highly stretchable silicone rubber nanocomposites incorporated with oleic acid‐modified Fe3O4 nanoparticles

“…By coating iron oxide nanoparticle filler with fatty acid, the elastic modulus of silicon rubber decreased 15 . The tensile stress of silicone rubber composites interpenetrated with spheroidal Al 2 O 3 and flaky BN increased from 0.65 to 1.60 MPa due to the improved dispersion and interfacial quality between fillers and the silicone rubber matrix 16 . Therefore, it is crucial to establish strong interfacial interaction between fillers and the silicone rubber matrix.…”