Enhanced positive temperature coefficient intensity and reproducibility with synergistic effect of 0-D and 2-D filler composites

Positive temperature coefficient (PTC) composites have received significant attention as electronic applications such as resettable fuses, safe batteries, self-regulating heating device and temperature sensors. Despite PTC composites preferred to industrial applications due to their easy processing, low density, good flexibility, and toughness, but poor reproducibility due to the conductive network randomly deconstructing or reconstructing in the molten state of polymer matrix delays the practical application. In particular, PTC intensity and reproducibility are important factors for application to temperature sensors. Herein, we present ethylene–vinyl acetate (EVA)-based PTC composites that demonstrate an enhanced intensity and reproducibility by controlling filler mobility and thermal expansion via combination of 0-D and 2-D carbon filler. A Carbon black (CB)/Exfoliated graphite (ExG)/EVA composite exhibited the high PTC intensity and superior reproducibility at repeated thermocycles. Furthermore, the CB/ExG/EVA composites exhibited a temperature sensitivity of approximately 14 times higher than that reported in another temperature sensor literature. The formation and inhibition of conducting networks on the controlled filler combination exhibited the synergistic effects of the 0-D and 2-D carbon fillers. The PTC composite with combination of 0-D and 2-D fillers can detect human skin temperature through real-time monitoring and showed an accuracy of 0.41 °C. This work provides a feasibility of PTC temperature sensor in specific applications that require relatively high temperature sensitivity and flexibility, such as monitoring the human body temperature.