The measurement and characterisation of small quantities of moisture in powders

It is well known that changes in atmospheric humidity can significantly affect the ease of recovery of stored powders. This is demonstrated, explained and an investigation of a technique to monitor the effects involved is carried out. The demonstration is by construction of powder shear tests at various humidities. The effects observed are explained in terms of the water vapour–surface interaction by use of common physical adsorption models. To devise an efficient monitoring technique the literature pertaining to moisture measurement is reviewed and an electrical conduction method is preferred. A mathematical model for flow of electrical current through a powder bed is developed and is shown to be reasonable.