Effect of Ambient Air Relative Humidity on the Surface Electric Potential Decay of Tribocharged Polypropylene and Polyvinyl Chloride Slabs

Ambient air humidity is known to be an important factor in the triboelectric charging of polymers. A study on the influence of this factor was conducted in a climatic test chamber on polypropylene (PP) and polyvinyl chloride (PVC) plates (110 mm x 110 mm x 4.5 mm) rubbed against aluminum (Al) parallelepiped bars (100 mm x 15 mm x 5 mm). The samples were left for at least 12 hours in the climatic test chamber at a fixed temperature (25 °C) and three different values of ambient air relative humidity (20%, 40%, and 80%), then rubbed against each other using a custom-designed linear tribometer. The tribocharged PP and PVC samples were then placed under an electrostatic probe to measure the decay of the electrical potential at their surface. The experimental results show that the ability of polymer plates to maintain the potential generated on their surface depend on the ambient conditions. A high relative humidity of the ambient air strongly deteriorated the capacity of PVC plates to hold the electric charge at their surface. Conversely, the PP plates showed a much better capacity to maintain the electrical charge acquired by tribocharging, regardless of the value of humidity in which the experiments were performed.