Lightweight and conductive carbon black/chlorinated poly(propylene carbonate) foams with a remarkable negative temperature coefficient effect of resistance for temperature sensor applications

In the current study, we fabricated lightweight and biodegradable conductive carbon black/chlorinated poly(propylene carbonate) (CB/CPPC) foams with a well-defined closed-cell structure by the combination of facile melt blending and the subsequent chemical foaming process. It was found that the foaming treatment could significantly lower the electrical percolation threshold from 2.48 vol% (solid composites) to 0.138 vol%. More interestingly, it was noted that the CB/CPPC foams exhibited a nearly-linear negative temperature coefficient (NTC) effect of resistance with increasing temperature from 25 degrees C to 70 degrees C, which was attributed to the gas expansion-induced thinning of cell walls and thereby a decreased distance between adjacent CB particles. The NTC effect of the CB/CPPC foams was more sensitive than that of most of the previously reported NTC composites. Moreover, the crosslinked CB/CPPC foams have both high sensitivity and good reproducibility of the NTC effect, which could well detect the change of temperature as shown in the demonstration experiments. The range of temperature detected by the CB/CPPC foams is from room temperature to 70 degrees C, which is ideal for wearable electronics and versatile temperature sensors in medical, food, and environment monitoring. The current study provides a facile route for large-scale preparation and practical application of NTC materials.