Optimization of flexible, low-loss, and temperature-stable strontium titanate–reinforced liquid silicone rubber composite for next-generation microwave applications

Flexible materials have become essential for emerging advanced wireless technologies, necessitating a thorough investigation of the material properties for suitable applications. This study explores a flexible strontium titanate (SrTiO3)-reinforced, platinum-cured liquid silicone rubber (LSR) composite for flexible microwave applications, including antennas, RF sensors, resonators, filters, and waveguides. The LSR-SrTiO3 composites were prepared with various filler contents (40, 50, and 60 phr) to tune and examine their material, dielectric, mechanical, and thermal properties. XRD and SEM analyses confirmed the distribution of the SrTiO3 nanoparticles within the LSR matrix. The measured dielectric constant increased by 33% at 20 Hz and 25% at 10 MHz, whereas the dielectric loss increased slightly, remaining in the order of 10−3 for maximum filler loading. An increment of ~43% increment was observed in the dielectric constant, accompanied by a loss of the order of 10−2 at X-band. A 37% reduction in the tensile strength was noticed, without compromising flexibility. The thermal decomposition temperature improved by 25% while the thermal expansion (CLTE) decreased to 22%, resulting in enhanced thermal stability. The results suggest that the 60 phr (maximum) reinforced LSR-SrTiO3 composite offers an optimal dielectric and thermal performance with acceptable mechanical flexibility, making it desirable for advanced flexible microwave applications.