Effect of thermosetting resin matrix on resistance-temperature stability of carbon fiber conductive composites

Carbon fiber conductive composites have been widely used as various electronic components due to their incomparable advantages compared with metal materials in lightweight, easy processing and especially the wide tunability of conductivity. However, negative temperature coefficient (NTC) effect or positive temperature coefficient (PTC) effect produced under the service temperature leads to the fluctuation of their resistance, thus making great effect on precision and limiting extensive applications. In this paper, mainly focusing on the effect of resin matrix on the conductive property and developing the resistance-temperature stable conductive composites, the various conductive composites were prepared by compounding thermoset resin with the hybrid fibers consisting of short carbon fiber (SCF) and short glass fiber (SGF) via changing the content and type of resin matrix respectively. The optical microscope and scanning electron microscope (SEM) images indicated SCF and SGF co-constructed the conductive nets. The temperature cycling testing results from the unsaturated polyester resin (UPR)-based composites showed that all the samples with different content of UPR exhibited the almost unchanged resistance when temperature was below glass transition temperature (T-g) of pure resin matrix, while exhibited the PTC effect as well as hysteresis loop when temperature was above T-g. In addition, the hysteresis loop became smaller and shifted to a higher temperature with the decrease of resin content in composite, meaning that lower resin content is responsible for the high resistance stability. More importantly, it reveals that there is a strong correlation between the resistance stability of composite and thermal property of resin matrix such as T-g. When bisphenol E cyanate (CE) with an over 200 degrees C T-g value is used as the resin matrix, the higher stability of conductive composite is achieved than that based on UPR and EP, and the average change in resistance is less than 1% during the heating-cooling test at 20 degrees C-180 degrees C.