Semiconducting flexible polymer matrix composites with tunable temperature profiles find use in consumer goods, robotics, aerospace, and energy sectors. However, the manufacturing cost is high due to the need for expensive conductive phases, such as carbon nanotubes, graphene, or metal nanoparticles. This study aims to use inexpensive conductive materials, such as carbon blacks and natural graphite in polydimethylsiloxane matrix to manufacture such composites. The composite samples prepared by the solution-mixing approach were tested for dispersibility, electrical conductivity, thermal responsiveness, and mechanical and morphological characteristics. They displayed non-wettable and low-energy surfaces (26 J/m²) and, hence, were prone to agglomeration at high carbon contents (>30%). Surfactant addition was employed to counteract the negative consequences of agglomeration. Adjusting the carbon content could modulate conductivity between 0 and 10.79 S/m. A typical composite with 3.17 S/m conductivity showed a surface temperature of 49.7°C under a load of 30 V. Compared to bare PDMS, mechanical properties were favorable; a composite with optimal conductivity and temperature response showed increases of 97.8% in elastic modulus and 197% in tear strength, despite a 50% decrease in tensile strength. The study highlights significant economic potential in manufacturing semiconductive flexible composites with desired temperature profiles.