Studies on composites based on HTV and RTV silicone rubber and carbon nanotubes for sensors and actuators

Nanofillers such as carbon nanotubes (CNT) are well known to significantly improve the properties of composites. In this work, CNTs were used as a reinforcing nanofiller in high-temperature vulcanized (HTV) silicone rubber, and room-temperature vulcanized (RTV) silicone rubber. At a low CNT content of 3 phr in HTV silicone rubber, the compressive and tensile moduli improved by 65% and 96%, respectively, and the resistance fell to 13k Omega. Similarly, at 3 phr of CNT in RTV silicone rubber, the compressive and tensile moduli improved by 110% and 105%, respectively, and the resistance fell to 0.4 k Omega. The improved properties were used for applications in piezo-electric actuation and piezo-resistive strain sensors. With increase in voltage supply from 2 kV to 12 kV at 2 phr CNT, the piezoelectric actuation displacement increases to 920% (RTV silicone elastomer slab) and 1025% (HTV silicone elastomer slab). In addition, the rubber-based piezoresistive strain sensors showed a higher gauge factor with RTV silicone rubber than HTV silicone rubber. The piezoresistive strain sensors showed >100% stretchability. A series of experiments demonstrate that the use of CNTs improves the reinforcing, electrical properties, actuation, and strain sensors based on RTV and HTV silicone composites.