Characterisation of electrostatic properties of powder coatings in relation with their industrial application

The aim of this work was to develop an experimental set-up allowing the measurement of tribo-charging during handling and transport of powders. The experimental set-up included a fluidisation unit, a transport pipe and two “Faraday cups” allowing continuous monitoring of particles charge. Several batches of industrial powder coatings were tested. The investigated parameters were the length and the fouling of the conveying pipe. The experimental device and procedure permitted to classify conveniently the tested powders according to their ability to be charged. More specially, a net difference between electrostatic properties of two powder primers, which behave very differently in the industrial application unit, was pointed out. Furthermore, it was established that tribo-charging is essentially governed by the nature of the flow conditioner added to powder coatings. The results showed that the net amount of acquired tribo-charge increases with the length of the conveying pipe. However the polarity of charges could change with the pipe fouling.