Poly(4-vinylpyridine)/carbon black composite as a humidity sensor

Poly(4-vinylpyridine) (PVP) was grafted onto carbon black (CB) to obtain a composite, which was further quaternized and crosslinked with bromobutane and 1,4-dibromobutane to prepare a resistive-type humidity sensitive material. The investigations on its electrical response to humidity revealed that it exhibited high conductivity even at very low humidity, and both ionic and electronic conduction contributed to its conductivity. The content of CB, quaternization and crosslinking reaction of PVP greatly affected the relative contributions of the two types of conduction, thus modulating the humidity sensitive properties of the composite. Under optimized conditions, the composite of CB and PVP exhibited a very wide sensing range of 0–97% RH, thus solving the problem of detecting low humidity with resistive-type polymeric humidity sensors.