Electrical and thermal phenomena in low-density polyethylene/carbon black composites near the percolation threshold

Low-density polyethylene (LDPE)/carbon black (CB) composites were fabricated via melt-compounding technique. The percolation threshold was found to be around 20 wt % CB, and an electrical network formed by conductive CB was proven by scanning electron microscopy investigation. Dielectric responses depicted an interfacial relaxation peak at 20 wt % CB content. LDPE/CB composites showed an electric field-dependent conductivity as and a hysteresis behavior around the percolation threshold region. The CB particles with high thermal conductivity increased the heat conductance of the LDPE/CB20 up to 56%. The dynamic mechanical analysis of the LDPE/CB composites exhibited a noticeable contribution of CB throughout the composites, increasing the storage and loss modulus. The physical interactions between CB particles in the filler network enhanced the thermal degradation of the LDPE/CB25 composite for more than 76°C. The maximum breakdown strength of the LDPE/CB composites appeared with an approximately 10% improvement for LDPE/CB5 than pure LDPE. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47043.     

Enhancement in electrical and thermal performance of high-temperature vulcanized silicone rubber composites for outdoor insulating applications

High-temperature vulcanized silicone rubber composites are highly desirable as outdoor insulating materials due to their immense thermal and electrical performance. The aim of this work is to study the role of co-combined fillers (modified fumed silica [MFS], titanium dioxide [TiO₂], with graphene [G]) on electrical and thermal properties of silicone rubber (S) composites. The dielectric response of S/MFS_10 phr and S/TiO₂_20 composites tailored with 2 phr G was characterized by broadband dielectric spectroscopy. The hybrid filler/composites were found to show higher thermal stability when 2 phr G was added. In addition, a low quantity of G filler was found to slightly increase the AC dielectric breakdown strength of the S/MFS_10 and S/TiO₂_20, where an improvement of 3 and 5% was found, respectively. Several steps were observed in the thermal decomposition of the S rubber composites by thermogravimetric analysis-Fourier-transform infrared spectroscopy. Our findings revealed great potentials for fabricating hybrid-filler/silicone rubber composites with enhanced electrical and thermal properties for outdoor insulating applications.