Fabrication and performance evaluation of the flexible positive temperature coefficient material for self-regulating thermal control

In this study, three kinds of newly flexible positive temperature coefficient (PTC) materials are fabricated by a simple preparation method. Due to intro-ducing the hybrid filler of carbon nanotube and carbon black, these materials exhibit remarkable PTC effect including the PTC intensity of more than four-orders magnitude and the resistivity-temperature coefficient of 154%/degrees C. The Curie points of PTC materials are regulated to room-temperature range by the low melting phase and influenced by melting onset temperatures of their solid-liquid phase change. With the help of transmission electron microscope, the micro-capsule structure of the phase change regions is observed, and the hybrid conductive fillers randomly distribute in the blend matrix to construct three-dimensional conductive network. Using the PTC materials as a heating element, the equilibrium temperature of the controlled device can be main-tained around their Curie point without any control method. Moreover, the adaptive thermal control effect becomes more obvious with the increase of ambient temperature and initial heating power. Furthermore, the thermal con-trol accuracy fluctuates within 0.15 degrees C without any external control method, and is improved to round 0.08 degrees C in combination with the switch control method. This study provides a new method for the thermal control of elec-tronic devices in the requirement of lightweight and miniaturization at low temperature environment.

Automated summary

Three types of newly flexible positive temperature coefficient (PTC) materials were prepared using a simple method. The materials exhibited a remarkable PTC effect, with a PTC intensity of over four orders magnitude and a resistivity-temperature coefficient of 154%/degrees C, due to the introduction of a hybrid filler of carbon nanotube and carbon black. The Curie points of the PTC materials were regulated to the room temperature range by a low melting phase and were influenced by the melting onset temperatures of their solid-liquid phase change. Observation with a transmission electron microscope revealed the micro-capsule structure of the phase change regions, in which hybrid conductive fillers randomly distributed in the blend matrix to form a three-dimensional conductive network. The use of these PTC materials as heating elements allowed the controlled devices to maintain an equilibrium temperature around their Curie point without the need for any control method. The adaptive thermal control effect became more pronounced with increasing ambient temperature and initial heating power. The thermal control accuracy fluctuated within 0.15 degrees C without any external control method and improved to 0.08 degrees C in combination with the switch control method. This study provides a new method for the thermal control of electronic devices in low temperature environments emphasizing lightweight and miniaturization.