A dew sensor based on modified carbon black and polyvinyl alcohol composites

Polyvinylpyrrolidone-grafted carbon black (CB-PVP) was prepared by a free radical polymerization reaction. The resultant CB-PVP could disperse well in water. Dew sensors based on CB/PVA (polyvinyl alcohol) and CB-PVP/PVA were obtained respectively, and their humidity switching properties were researched. Thermal annealing was used to improve the stability of the sensitive films effectively. Both CB/PVA and CB-PVP/PVA sensors showed obvious humidity switching properties, and CB-PVP/PVA sensor performed properties better than CB/PVA sensor. In the case of the 6 wt% CB-PVP/PVA film, the resistance was about 10 kΩ below 80% relative humidity (RH) and increased sharply over 85% RH, with a resistance of 170 kΩ at 100% RH. The conductive mechanism of the CB-PVP/PVA materials was discussed through direct current reverse polarity method. The CB-PVP/PVA composite is a promising dew sensing material.